WO2022044540A1

WO2022044540A1 - Solid oxide fuel cell and method for manufacturing the same

Info

Publication number: WO2022044540A1
Application number: PCT/JP2021/024909
Authority: WO
Inventors: 李新宇
Original assignee: 太陽誘電株式会社
Priority date: 2020-08-31
Filing date: 2021-07-01
Publication date: 2022-03-03

Abstract

This solid oxide fuel cell is characterized by comprising: an electrolyte layer containing a solid oxide having oxide ion conductivity; an intermediate layer provided on the electrolyte layer and having oxide ion conductivity; and a cathode provided on the intermediate layer. The solid oxide fuel cell is further characterized in that: the intermediate layer is provided with a plurality of recesses and protrusions on the cathode-side surface thereof, which are aligned in the two-dimensional direction when observed in plan view; and the intermediate layer is provided with a plurality of recesses and protrusions on the electrolyte layer-side surface thereof, the recesses and protrusions provided so as follow the plurality of recesses and protrusions on the cathode-side surface.　

Description

Solid oxide fuel cell and its manufacturing method

The present invention relates to a solid oxide fuel cell and a method for manufacturing the same.

The solid oxide fuel cell has a structure in which a solid oxide electrolyte is sandwiched between an anode and a cathode. The cathode used in such a solid oxide fuel cell may react with a solid oxide-based electrolyte. Therefore, in order to suppress the reaction between the solid oxide-based electrolyte and the cathode, a technique of providing an anti-reaction film such as GDC as an intermediate layer between the cathode and the solid oxide-based electrolyte is disclosed (for example, patent). See Document 1).

JP-A-2017-504946

However, if an intermediate layer is provided, the reaction resistance during power generation may increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a solid oxide fuel cell capable of reducing reaction resistance and a method for producing the same.

The solid oxide fuel cell according to the present invention has an electrolyte layer containing a solid oxide having oxide ion conductivity, an intermediate layer provided on the electrolyte layer and having oxide ion conductivity, and the intermediate layer. The intermediate layer is provided with a cathode provided above, and the intermediate layer is provided with a plurality of irregularities on the surface on the cathode side so as to be arranged in a two-dimensional direction in a plan view, and the intermediate layer is on the side of the electrolyte layer. The surface is characterized in that a plurality of irregularities are provided along the plurality of irregularities on the surface on the cathode side.

In the solid oxide fuel cell, the unevenness on the surface of the intermediate layer on the cathode side may be formed in the form of particles.

The vertical distance a between the peak and the valley may be 0.05 μm or more and 3 μm or less in the unevenness of the surface on the cathode side of the intermediate layer of the solid oxide fuel cell.

The horizontal distance b between the peaks may be 0.1 μm or more and 5 μm or less in the unevenness of the surface on the cathode side of the intermediate layer of the solid oxide fuel cell.

In the unevenness of the surface on the cathode side of the intermediate layer of the solid oxide fuel cell, a / b, which is the ratio of the vertical distance a between the peaks and valleys and the horizontal distance b between the peaks and peaks, is 1 /. It may be 10 or more and 20/1 or less.

In the solid oxide fuel cell, a plurality of irregularities may be provided on the surface of the electrolyte layer on the side of the intermediate layer so as to follow the irregularities on the surface of the intermediate layer on the side of the electrolyte layer.

The vertical distance a'between peaks and valleys may be 0.05 μm or more and 3 μm or less in the unevenness of the surface of the electrolyte layer of the solid oxide fuel cell on the intermediate layer side.

The horizontal distance b'b between peaks may be 0.1 μm or more and 5 μm or less in the unevenness of the surface of the electrolyte layer of the solid oxide fuel cell on the intermediate layer side.

In the unevenness of the surface of the electrolyte layer on the intermediate layer side of the solid oxide fuel cell, a'/ b, which is the ratio of the vertical distance a'of the peak and the valley to the horizontal distance b'of the peak and the peak. ´ may be 1/10 or more and 20/1 or less.

In the solid oxide fuel cell, the vertical distance a between the peak and the valley in the unevenness of the surface on the cathode side of the intermediate layer and the electrolyte layer side of the intermediate layer on the surface on the intermediate layer side of the electrolyte layer. The vertical distance a'between peaks and valleys in a plurality of irregularities provided along the unevenness on the surface of the surface may have a relationship of 0.5≤a / a'≤1.

In the solid oxide fuel cell, the horizontal distance b between the peaks on the uneven surface of the cathode side of the intermediate layer and the electrolyte layer side of the intermediate layer on the surface of the electrolyte layer on the intermediate layer side. The horizontal distance b'b.

In the solid oxide fuel cell, the mountain along the unevenness on the surface of the intermediate layer on the cathode side and the unevenness on the surface of the intermediate layer on the side of the intermediate layer along the unevenness of the surface of the intermediate layer on the side of the electrolyte layer. The vertical distance from the mountain corresponding to the mountain in the unevenness provided as described above may be 10 nm or more and 3 μm or less.

The other solid oxide fuel cell according to the present invention has an electrolyte layer containing a solid oxide having oxide ion conductivity, an intermediate layer provided on the electrolyte layer and having oxide ion conductivity, and the above. A cathode provided on the intermediate layer is provided, and the intermediate layer is formed along the unevenness provided on the surface of the electrolyte layer on the intermediate layer side. In the intermediate layer, the electrolyte layer is provided. From the side to the cathode side, a plurality of voids are formed so as to be arranged at intervals along a predetermined line.

In the intermediate layer of the solid oxide fuel cell, the number density of the voids in the convex portion with respect to the cathode side may be larger than the number density of the voids in the concave portion with respect to the cathode side.

In the solid oxide fuel cell, the average diameter of the voids may be 50 nm or less.

In the solid oxide fuel cell, the unevenness of the electrolyte layer may be provided so as to be arranged in a two-dimensional direction in a plan view on the surface on the intermediate layer side.

In the solid oxide fuel cell, the intermediate layer may be a material in which an additive is added to ceria.

In the method for manufacturing a solid oxide fuel cell according to the present invention, an electrolyte layer green sheet is produced by applying a slurry containing an oxide ion conductive material powder, and the electrolyte layer is placed on the electrolyte layer green sheet. By applying and firing a slurry containing the oxide ion conductive material powder having a D50% particle size smaller than the D50% particle size of the oxide ion conductive material powder of the green sheet and the resin particles, the green sheet is fired. In the step of forming an electrolyte layer having irregularities on the surface, an intermediate layer having oxide ion conductivity and no cathode activity is formed on the electrolyte layer by the PVD method, and is formed on the intermediate layer. When the cathode is formed and the intermediate layer is formed by the PVD method, a plurality of voids are formed so as to be arranged at intervals along a predetermined line from the electrolyte layer side to the cathode side. It is characterized in that at least one of the film forming rate and the substrate heating temperature is controlled.

According to the present invention, it is possible to provide a solid oxide fuel cell capable of reducing reaction resistance and a method for producing the same.

It is a schematic cross-sectional view which illustrates the laminated structure of a fuel cell. FIG. 6 is an enlarged cross-sectional view illustrating details of a support, a mixed layer, and an anode. (A) is an enlarged cross-sectional view from the electrolyte layer to the cathode, and (b) is a plan view of the intermediate layer. It is an enlarged sectional view from an electrolyte layer to a cathode. It is a figure for demonstrating each dimension. It is an enlarged view which made the intermediate layer schematically enlarged. It is a figure for demonstrating the boundary between the concave part 41 and the convex part 42. It is a figure which illustrates the flow of the manufacturing method of a fuel cell. It is a figure which illustrates the electrolyte layer green sheet and the green sheet for an uneven layer in a laminating process.

Hereinafter, embodiments will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic cross-sectional view illustrating a laminated structure of a solid oxide fuel cell 100. As illustrated in FIG. 1, as an example, the fuel cell 100 has a structure in which a mixed layer 20, an anode 30, an electrolyte layer 40, an intermediate layer 50, and a cathode 60 are laminated in this order on a support 10. A plurality of fuel cells 100 may be stacked to form a fuel cell stack.

The electrolyte layer 40 is a dense layer having a solid oxide having oxide ion conductivity as a main component and having gas impermeable property. The electrolyte layer 40 preferably contains, as a main component, Scandia-yttria-stabilized zirconium oxide (ScYSZ), YSZ (yttria-stabilized zirconium oxide), GDC (Gd-doped ceria) in which Gd (gadolinium) is doped in CeO ₂ . .. When ScYSZ is used, the concentration of Y ₂ O ₃ + Sc ₂ O ₃ has the highest oxide ion conductivity between 6 mol% and 15 mol%, and it is desirable to use a material having this composition. The thickness of the electrolyte layer 40 is preferably 20 μm or less, more preferably 10 μm or less. The thinner the electrolyte, the better, but in order to manufacture it so that the gas on both sides does not leak, a thickness of 1 μm or more is desirable.

The cathode 60 is an electrode having electrode activity as a cathode, and has electron conductivity and oxide ion conductivity. For example, the cathode 60 is mainly composed of a ceramic material having electron conductivity and oxide ion conductivity. As the ceramic material, for example, a LaCoO ₃ -based material, a LaMnO ₃ -based material, a LaFeO ₃ -based material, or the like can be used. For example, LSC (lantern strontium cobaltite) or the like can be used as the LaCoO ₃ system material. LSC is _LaCoO3 doped with Sr (strontium).

The intermediate layer 50 contains a component that prevents the reaction between the electrolyte layer 40 and the cathode 60 as a main component. The constituent material of the intermediate layer 50 is different from the constituent material of the electrolyte layer 40. The intermediate layer 50 has oxide ion conductivity, but does not have electrode activity as a cathode. For example, the intermediate layer 50 has a structure in which an additive is added to ceria (CeO ₂ ). The additives are not particularly limited. For example, the intermediate layer 50 contains GDC (for example, Ce _0.8 Gd _0.2 O _2-x ) or the like as a main component. As an example, when the electrolyte layer 40 contains ScYSZ and the cathode 60 contains LSC, the intermediate layer 50 prevents the following reactions.
Sr + ZrO ₂ → SrZrO ₃
La + ZrO ₃ → La ₂ Zr ₂ O ₇

FIG. 2 is an enlarged cross-sectional view illustrating the details of the support 10, the mixed layer 20, and the anode 30. As illustrated in FIG. 2, the support 10 is a member that has gas permeability and can support the mixed layer 20, the anode 30, the electrolyte layer 40, the intermediate layer 50, and the cathode 60. The support 10 is a metal porous body containing a metal as a main component, and is, for example, a porous body of an Fe—Cr alloy.

The anode 30 is an electrode having electrode activity as an anode, and has an electrode skeleton made of a ceramic material. The electrode skeleton does not contain metal components. In this configuration, the decrease in porosity of the anode due to the coarsening of the metal component is suppressed during firing in a high-temperature reducing atmosphere. Further, alloying with the metal component of the support 10 is suppressed, and deterioration of the catalytic function is suppressed.

The electrode skeleton of the anode 30 has electron conductivity and oxide ion conductivity. The anode 30 contains the electron conductive ceramics 31. As the electron conductive ceramics 31, for example, it is a perovskite-type oxide whose composition formula is represented by ABO ₃ , and A site is at least one selected from the group of Ca, Sr, Ba, La, and B site is. A perovskite-type oxide, which is at least one selected from Ti, Cr, Ni, Mg, and Co, can be used. The molar ratio of A site to B site may be B ≧ A. Specifically, as the electron conductive ceramics 31, a _LaCrO3 system material _, an SrTiO3 system material, or the like can be used.

Further, the electrode skeleton of the anode 30 contains the oxide ion conductive ceramics 32. The oxide ion conductive ceramics 32 is ScYSZ or the like. For example, it is preferable to use ScYSZ having a composition range of 5 mol% to 16 mol% for scandia (Sc ₂ O ₃ ) and 1 mol% to 3 mol% for itria (Y ₂ O ₃ ). ScYSZ in which the total amount of scandia and ittoria added is 6 mol% to 15 mol% is more preferable. This is because the oxide ion conductivity is the highest in this composition range. The oxide ion conductive ceramics 32 is, for example, a material having an oxide ion transport number of 99% or more. GDC or the like may be used as the oxide ion conductive ceramics 32. In the example of FIG. 2, the same solid oxide as the solid oxide contained in the electrolyte layer 40 is used as the oxide ion conductive ceramics 32.

As illustrated in FIG. 2, in the anode 30, for example, the electron conductive ceramics 31 and the oxide ion conductive ceramics 32 form an electrode skeleton. A plurality of voids are formed by this electrode skeleton. An anode catalyst is supported on the surface of the electrode skeleton in the void portion. Therefore, in the electrode skeleton formed spatially continuously, a plurality of anode catalysts are spatially dispersed and arranged. It is preferable to use a composite catalyst as the anode catalyst. For example, as the composite catalyst, it is preferable that the oxide ion conductive ceramics 33 and the catalyst metal 34 are supported on the surface of the electrode skeleton. Examples of the oxide ion conductive ceramics 33 include Y-doped BaCe _1-x Zr _x O ₃ (BCZY, x = 0-1) and Y-doped SrCe _1-x Zr _x O ₃ (SCZY,). x = 0 to 1), Sr-doped LaScO ₃ (LSS), GDC and the like can be used. As the catalyst metal 34, Ni or the like can be used. The oxide ion conductive ceramics 33 may have the same composition as the oxide ion conductive ceramics 32, but may have a different composition. The metal that functions as the catalyst metal 34 may be in the form of a compound when no power is generated. For example, Ni may be in the form of NiO (nickel oxide). During power generation, these compounds are reduced by the reducing fuel gas supplied to the anode 30 and take the form of a metal that functions as an anode catalyst.

The mixed layer 20 contains a metal material 21 and a ceramic material 22. In the mixed layer 20, the metal material 21 and the ceramic material 22 are randomly mixed. Therefore, the structure in which the layer of the metal material 21 and the layer of the ceramic material 22 are laminated is not formed. The mixed layer 20 is also porous, and a plurality of voids are formed. The metal material 21 is not particularly limited as long as it is a metal. In the example of FIG. 2, the same metal material as the support 10 is used as the metal material 21. For example, as the ceramic material 22, ScYSZ, GDC, SrTiO ₃ -based material, LaCrO ₃ -based material, or the like can be used. Since the SrTiO ₃ system material and the LaCrO ₃ system material have high electron conductivity, the ohmic resistance in the mixed layer 20 can be reduced.

The fuel cell 100 generates electricity by the following actions. An oxygen-containing oxidant gas such as air is supplied to the cathode 60. In the cathode 60, due to the effect of the electrode activity of the cathode 60, oxygen reaching the cathode 60 reacts with electrons supplied from an external electric circuit to form oxide ions. The oxide ion conducts through the intermediate layer 50 and the electrolyte layer 40 and moves to the anode 30 side. On the other hand, a fuel gas containing hydrogen such as hydrogen gas and reforming gas is supplied to the support 10. The fuel gas reaches the anode 30 via the support 10 and the mixed layer 20. The hydrogen that reaches the anode 30 emits electrons at the anode 30 due to the effect of the electrode activity of the anode 30, and reacts with the oxide ion conducting the electrolyte layer 40 from the cathode 60 side to water (H ₂ O). )become. The emitted electrons are taken out by an external electric circuit. The electrons taken out to the outside are supplied to the cathode 60 after performing electrical work. Power generation is performed by the above action.

In the fuel cell 100 provided with the intermediate layer 50, the place that most contributes to the cathode reaction is the interface where the intermediate layer 50 and the cathode 60 come into contact with each other. The area of this contact interface is inversely proportional to the reaction resistance. Therefore, the larger the contact area per unit area, the lower the reaction resistance per unit area. From the above, improving the contact area between the intermediate layer 50 and the cathode 60 is an issue for the development of the fuel cell 100.

Therefore, the fuel cell 100 according to the present embodiment has a structure for improving the contact area between the intermediate layer 50 and the cathode 60. FIG. 3A is an enlarged cross-sectional view from the electrolyte layer 40 to the cathode 60. As illustrated in FIG. 3A, the intermediate layer 50 is formed so that a plurality of concave portions 51 and convex portions 52 are alternately arranged on the surface on the cathode 60 side. The convex portion 52 has a shape that protrudes and curves toward the cathode 60 side. As illustrated in FIG. 3B, the concave portions 51 and the convex portions 52 are arranged alternately not only in one direction but also in a two-dimensional direction in the plane of the intermediate layer 50. The two-dimensional directions do not necessarily have to be orthogonal in the plane of the intermediate layer 50, and may intersect. In a plan view with respect to the intermediate layer 50, the convex portions 52 are in the form of particles and are randomly arranged in the plane of the intermediate layer 50. The scales of FIGS. 3 (a) and 3 (b) are different.

Since the intermediate layer 50 has irregularities on the surface on the cathode 60 side, the cathode 60 also has irregularities along the irregularities of the intermediate layer 50. That is, as illustrated in FIG. 4, the cathode 60 is provided with a convex portion 61 projecting toward the intermediate layer 50 at the position where the concave portion 51 of the intermediate layer 50 is formed in FIG. 3 (a), and is provided with FIG. 3 (a). ), The concave portion 62 is provided at the position where the convex portion 52 of the intermediate layer 50 is formed. Therefore, the area of the contact interface between the intermediate layer 50 and the cathode 60 becomes large. Further, since the directions in which the irregularities of the intermediate layer 50 and the cathode 60 are arranged are arranged in the two-dimensional direction in the plane, the area of the contact interface between the intermediate layer 50 and the cathode 60 becomes larger. In this configuration, the reaction field per unit area increases, and the reaction resistance of the cathode 60 can be reduced.

In order to reduce the reaction resistance of the cathode 60, it is desirable that the distance between the electrolyte layer 40 and the cathode 60 is short. Therefore, unevenness is also formed on the surface of the electrolyte layer 40 on the cathode 60 side. The surface of the intermediate layer 50 on the electrolyte layer 40 side is also formed so as to follow the shape of the unevenness of the electrolyte layer 40. For example, as illustrated in FIG. 4, in the electrolyte layer 40, a plurality of concave portions 41 and convex portions 42 are alternately formed on the surface on the cathode 60 side. In a plan view with respect to the intermediate layer 50 and the electrolyte layer 40, the positions of the concave portion 51 and the concave portion 41 in FIG. 3A are substantially the same, and the positions of the convex portion 52 and the convex portion 42 in FIG. 3A are substantially the same. Therefore, the concave portion 41 and the convex portion 42 are not arranged in only one direction, but are also arranged in the two-dimensional direction in the plane of the electrolyte layer 40. Therefore, in the plan view of the electrolyte layer 40, the convex portions 52 are in the form of particles and are randomly arranged in the plane of the electrolyte layer 40. As described above, in the plan view with respect to the electrolyte layer 40, the positions of the concave portion 51 and the concave portion 41 are substantially the same, and the positions of the convex portion 52 and the convex portion 42 are substantially the same. Therefore, the positions of the convex portion 61 and the concave portion 41 are substantially the same. Since the positions of the concave portion 62 and the convex portion 42 are substantially the same, the intermediate layer 50 is prevented from being partially thickened, and the distance between the electrolyte layer 40 and the cathode 60 is shortened. Therefore, the reaction resistance of the cathode 60 can be reduced.

FIG. 5 is a diagram for explaining each size of the concave portion 51 and the convex portion 52 of the intermediate layer 50. In order to measure each size, the fuel cell 100 is embedded in resin and polished to the extent that the laminated cross section of each layer can be obtained. After that, CP (Cross section polisher) processing is performed on the polished surface to obtain a clean cross section. After that, each size can be measured by observing the cross section with SED-EDS.

As illustrated in FIG. 5, the dimension a is the vertical distance between the peak and the valley in the concave-convex structure on the cathode 60 side of the intermediate layer 50, and the convex portion 52 adjacent to the bottom of the concave portion 51 in FIG. 3 (a). The height to the apex of the fuel cell 100 (height in the stacking direction of each layer of the fuel cell 100). For the dimension a, the CP-processed cross section is observed with an SEM (scanning electron microscope), several photographs are taken, and the vertical distance between the peak and the valley in the uneven structure on the cathode 60 side of the intermediate layer 50 is 20. It is the average value when measured at a location.

If the dimension a is large, the electrolyte layer 40 will be apparently thick. Therefore, it is preferable to set an upper limit on the dimension a. For example, the dimension a is preferably 3 μm or less, more preferably 1 μm or less, and further preferably 0.5 μm or less.

On the other hand, if the dimension a is small, the cathode material of the cathode 60 may not easily enter the uneven structure of the intermediate layer 50. Therefore, it is preferable to set a lower limit for the dimension a. For example, the dimension a is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.15 μm or more.

As illustrated in FIG. 5, the dimension a'is the vertical distance between the peak and the valley in the concave-convex structure on the cathode 60 side in the electrolyte layer 40, and is the apex of the convex portion 42 adjacent to the bottom of the concave portion 41 in FIG. (Height in the stacking direction of each layer of the fuel cell 100). For the dimension a', the CP-processed cross section was observed by SEM, several photographs were taken, and the vertical distance between the peak and the valley in the uneven structure on the cathode 60 side of the electrolyte layer 40 was measured at 20 locations. The average value of the cases. In order for the dimension a of the intermediate layer 50 to be within a predetermined range, it is preferable that the dimension a'of the underlying electrolyte layer 40 is also substantially the same value. Therefore, it is preferable that the dimension a'is within the range of 0.05 μm or more and 3 μm or less.

When the intermediate layer 50 becomes thicker, the unevenness of the intermediate layer 50 becomes flatter than the unevenness of the electrolyte layer 40. Therefore, it is preferable that the intermediate layer 50 is thin. Further, by thinning the intermediate layer 50, the uneven shape of the intermediate layer 50 substantially matches the uneven shape of the electrolyte layer 40. That is, a / a'= 1. As the intermediate layer 50 becomes thicker, a / a'becomes smaller. Therefore, when a / a'<0.5, the effect of increasing the contact area due to the uneven structure may not be obtained. Therefore, it is better to provide an appropriate range for a / a', preferably a / a'≧ 0.5, and preferably a / a'≦ 1. Since the unevenness of the intermediate layer 50 is formed by the unevenness of the electrolyte layer 40, a / a'> 1 is unlikely to occur.

Next, as illustrated in FIG. 5, the dimension b is the horizontal distance between the peaks in the concave-convex structure on the cathode side of the intermediate layer 50, and the convex portion adjacent to the convex portion 52 in FIG. 3 (a). The distance to 52. The dimension b is the case where the CP-processed cross section is observed by SEM, several photographs are taken, and the vertical distance between the peak and the valley in the uneven structure on the cathode 60 side of the intermediate layer 50 is measured at 20 locations. The average value of.

When the dimension b is large, the number of uneven structures on the surface of the intermediate layer 50 on the cathode 60 side is reduced. Therefore, it is preferable to set an upper limit on the dimension b. For example, the dimension b is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 1 μm or less.

On the other hand, if the dimension b is small, the cathode material of the cathode 60 may not easily enter the uneven structure of the intermediate layer 50. Therefore, it is preferable to set a lower limit for the dimension b. For example, the dimension b is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more.

As illustrated in FIG. 5, the dimension b'is the horizontal distance between the peaks in the concave-convex structure on the cathode 60 side in the electrolyte layer 40, and is the apex of the convex portion 42 adjacent to the bottom of the concave portion 41 in FIG. The distance to. The dimension b'is observed by SEM on the CP-processed cross section, and several photographs are taken. The dimension b'is an average value when the horizontal distance between the peaks in the uneven structure on the cathode 60 side of the electrolyte layer 40 is measured at 20 points. In order for the dimension b of the intermediate layer 50 to be within a predetermined range, it is preferable that the dimension b'of the underlying electrolyte layer 40 also has substantially the same value. Therefore, it is preferable that the dimension b'is within the range of 0.1 μm or more and 5 μm or less. Further, it is preferable that the unevenness of the intermediate layer 50 has the same shape as the unevenness of the electrolyte layer 40, and the closer to the same shape, the closer to b / b'= 1. Further, it is considered that the effect of increasing the contact area with the cathode due to the uneven structure can be obtained by having the same shape, and it is preferable that b / b'≧ 0.5, and b / b'≦ 1 preferable. Since the unevenness of the intermediate layer 50 is formed by the unevenness of the electrolyte layer 40, b / b'> 1 is unlikely to occur.

Further, the higher the value of a / b, the more the cathode material is filled in the valley portion. In the present embodiment, a / b is preferably 1/10 or more, more preferably 1/1 or more, and further preferably 5/1 or more. On the other hand, if the value of a / b is too high, the structure of the cathode 60 is likely to collapse when printing the cathode 60. Therefore, it is preferable to set an upper limit on a / b. In the present embodiment, a / b is preferably 20/1 or less, more preferably 15/1 or less, and even more preferably 10/1 or less.

As illustrated in FIG. 5, the dimension c is the vertical distance between the peak in the uneven structure of the intermediate layer 50 and the peak of the underlying electrolyte layer 40. Therefore, the dimension c is the distance between the apex of the convex portion 42 in FIG. 4 and the apex of the convex portion 52 in FIG. 3 (a) in the stacking direction. For dimension c, observe the CP-processed cross section with SEM, take pictures at several places, and set the vertical distance between the mountain in the uneven structure of the intermediate layer 50 and the mountain of the underlying electrolyte layer 40 at 20 places. It is the average when measured.

If the dimension c is large, the resistance value when ions are diffused may improve. Therefore, it is preferable to set an upper limit on the dimension c. In the present embodiment, the dimension c is preferably 3 μm or less, more preferably 2 μm or less, and further preferably 1 μm or less. Further, if the dimension c is too small, it becomes difficult to cover the entire uneven surface of the electrolyte layer 40. Therefore, it is preferable to set a lower limit for the dimension c. In the present embodiment, the dimension c is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 30 nm or more.

(Second Embodiment)
By the way, since the intermediate layer 50 is provided for the purpose of preventing the reaction between the electrolyte layer 40 and the cathode 60, the intermediate layer 50 is made of a material different from that of the electrolyte layer 40. Therefore, there is a difference between the thermal expansion rate of the electrolyte layer 40 and the thermal expansion rate of the intermediate layer 50. When the fuel cell 100 repeatedly starts and stops power generation, the fuel cell 100 repeatedly raises and lowers the temperature, and the intermediate layer 50 may be peeled off from the electrolyte layer 40 due to the difference in thermal expansion rate.

Therefore, the intermediate layer 50 according to the second embodiment has a structure that suppresses peeling from the electrolyte layer 40 even if the fuel cell 100 repeatedly raises and lowers the temperature. FIG. 6 is an enlarged view schematically an enlarged view of the intermediate layer 50. As illustrated in FIG. 6, a plurality of voids 53 are formed in the intermediate layer 50. The plurality of voids 53 are formed in the intermediate layer 50 so as to be arranged at predetermined intervals along a predetermined line from the convex portion 42 of the electrolyte layer 40 toward the cathode 60. That is, the arrangement of the plurality of voids 53 forms a columnar shape. For example, in the cross section of the intermediate layer 50 in the stacking direction, a plurality of voids 53 are lined up at predetermined intervals on the radiation spreading toward the cathode 60 centering on the top of the convex portion 42.

The void 53 formed in the intermediate layer 50 absorbs stress caused by the difference in thermal expansion rate between the electrolyte layer 40 and the intermediate layer 50. Therefore, even if the stress is generated, it is relaxed by the void 53. As a result, the resistance to the temperature cycle of the fuel cell 100 is improved, and the peeling of the intermediate layer 50 from the electrolyte layer 40 is suppressed.

Since the region other than the void 53 in the intermediate layer 50 is dense, oxide ions can move in the dense region. Therefore, the conductivity of oxide ions in the intermediate layer 50 is maintained at a high level. Further, since the voids 53 are provided at predetermined intervals without penetrating from the electrolyte layer 40 to the cathode 60, mutual diffusion between the electrolyte layer 40 and the cathode 60 is suppressed. Therefore, the intermediate layer 50 can maintain its function as a reaction prevention layer.

In the intermediate layer 50, the void 53 is mainly formed in the convex portion 42. That is, the number density of the voids 53 in the convex portion 42 is higher than the number density of the voids 53 in the concave portion 41.

Here, the boundary between the concave portion 41 and the convex portion 42 will be described with reference to FIG. 7. The concave portion 41 and the convex portion are formed by the angle α between the straight line a1 perpendicular to the tangent line b1 on the surface along the surface of the convex portion 42 and the straight line a2 perpendicular to the tangent line b2 on the surface beyond the mountain of the convex portion 42. Define the boundary with 42. The region where the angle α between the straight line a1 and the straight line a2 is 120 ° or less is defined as the convex portion 42, and the other portion is defined as the concave portion 41.

Each void 53 has a substantially spherical shape. If each void 53 is large, the number of voids 53 from the electrolyte layer 40 to the cathode 60 may be reduced, and the stress relaxation effect may be reduced. Therefore, it is preferable to set an upper limit on the average diameter of each void 53. For example, the average diameter of the void 53 is preferably 50 nm or less, more preferably 30 nm or less, and further preferably 10 nm or less. The diameter of the void 53 is the diameter when each void 53 is approximated to be spherical in the cross-sectional photograph. For example, the diameters of 20 or more voids 53 are measured in the field of view of a TEM (transmission electron microscope) image, and the averaged value is taken as the average diameter.

If each void 53 is too small, the void 53 may not be able to sufficiently absorb stress. Therefore, it is preferable to set a lower limit for the average diameter of each void 53. For example, the average diameter of the void 53 is preferably 1 nm or more, more preferably 3 nm or more, and further preferably 5 nm or more.

If the number of voids 53 from the electrolyte layer 40 to the cathode 60 is small per one convex portion 52, the stress relaxation effect may be small. Therefore, it is preferable to set a lower limit on the average value (per one convex portion 52) of the number of voids 53 from the electrolyte layer 40 to the cathode 60. For example, the average value is preferably 100 or more, more preferably 200 or more, and further preferably 300 or more.

If the number of voids 53 from the electrolyte layer 40 to the cathode 60 is large, it may be difficult for oxide ions to pass through. Therefore, it is preferable to set an upper limit on the average value of the number of voids 53 from the electrolyte layer 40 to the cathode 60. For example, the average value is preferably 5000 or less, more preferably 4000 or less, and further preferably 3000 or less.

If the average spacing of the voids 53 in the direction in which the voids 53 are lined up is too short, it may be difficult for oxide ions to pass through. Therefore, it is preferable to set a lower limit for the average spacing of the voids 53 in the direction in which the voids 53 are lined up. For example, the average spacing of the voids 53 is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more.

On the other hand, if the average spacing of the voids 53 in the direction in which the voids 53 are lined up is too long, the number of voids 53 may decrease and the effect of relieving stress may not be obtained. Therefore, it is preferable to set an upper limit on the average spacing of the voids 53 in the direction in which the voids 53 are lined up. For example, the average spacing of the voids 53 is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less.

Hereinafter, a method for manufacturing the fuel cell 100 according to the first embodiment and the second embodiment will be described. FIG. 8 is a diagram illustrating a flow of a manufacturing method of the fuel cell 100.

(Process for manufacturing support material) (S1)
As materials for the support, metal powder (for example, particle size of 10 μm to 100 μm), plasticizer (for example, adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), solvent (toluene, 2-propanol (toluene, 2-propanol). IPA), 1-butanol, turpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on the viscosity), vanishing material (organic substance), binder (PVB, acrylic resin, ethyl cellulose, etc.) are mixed to make a slurry. .. The support material is used as a material for forming the support 10. The volume ratio of the organic component (disappearing material, binder solid content, plasticizer) to the metal powder is, for example, in the range of 1: 1 to 20: 1, and the amount of the organic component is adjusted according to the porosity.

(Making step of material for mixed layer) (S1)
As the material for the mixed layer, the ceramic material powder (for example, the particle size is 100 nm to 10 μm) which is the raw material of the ceramic material 22 and the small particle size metal material powder (for example, the particle size is 1 μm to 10 μm) which is the raw material of the metal material 21. ), Solvent (toluene, 2-propanol (IPA), 1-butanol, turpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on the viscosity), plasticizer (for example, to adjust the adhesion of the sheet). (Adjusted from 1 wt% to 6 wt%), vanishing material (organic substance), and binder (PVB, acrylic resin, ethyl cellulose, etc.) are mixed to make a slurry. The volume ratio of the organic component (disappearing material, binder solid content, plasticizer) to the ceramic material powder and the metal material powder is, for example, in the range of 1: 1 to 5: 1, and the amount of the organic component is adjusted according to the porosity. adjust. Further, the pore diameter of the void is controlled by adjusting the particle size of the vanishing material. The ceramic material powder may contain an electron conductive material powder and an oxide ion conductive material powder. In this case, the volume ratio of the electron conductive material powder and the oxide ion conductive material powder is preferably in the range of, for example, 1: 9 to 9: 1. Further, even if an electrolyte material ScYSZ, GDC or the like is used instead of the electron conductive material powder, the interface is not peeled off and the cell can be manufactured. However, from the viewpoint of reducing the ohmic resistance, it is preferable to mix the electron conductive material powder and the metal powder.

(Process for manufacturing anode material) (S1)
As the material for the anode, the ceramic material powder constituting the electrode skeleton, the solvent (toluene, 2-propanol (IPA), 1-butanol, turpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on the viscosity), plasticizer. An agent (for example, adjusted from 1 wt% to 6 wt% to adjust the adhesion of the sheet), a vanishing material (organic substance), and a binder (PVB, acrylic resin, ethyl cellulose, etc.) are mixed to form a slurry. As the ceramic material powder constituting the electrode skeleton, the electron conductive material powder (for example, the particle size is 100 nm to 10 μm) which is the raw material of the electron conductive ceramics 31 and the oxide ion conduction which is the raw material of the oxide ion conductive ceramics 32. A ceramic material powder (for example, a particle size of 100 nm to 10 μm) may be used. The volume ratio of the organic component (disappearing material, binder solid content, plasticizer) to the electron conductive material powder is, for example, in the range of 1: 1 to 5: 1, and the amount of the organic component is adjusted according to the porosity. Further, the pore diameter of the void is controlled by adjusting the particle size of the vanishing material. The volume ratio of the electron conductive material powder and the oxide ion conductive material powder is, for example, in the range of 3: 7 to 7: 3.

(Process for Fabricating Material for Electrolyte Layer) (S1)
As the material for the electrolyte layer, an oxide ion conductive material powder (for example, ScYSZ, YSZ, GDC, etc., having a particle size of D50% = 10 nm to 1000 nm), a solvent (toluene, 2-propanol (IPA), 1- Butanol, turpineol, butyl acetate, ethanol, etc., 20 wt% to 30 wt% depending on viscosity), plasticizer (eg, adjusted to 1 wt% to 6 wt% to adjust sheet adhesion), and binder (PVB, Acrylic resin, ethyl cellulose, etc.) are mixed to make a slurry. The volume ratio of the organic component (binder solid content, plasticizer) to the oxide ion conductive material powder is, for example, in the range of 6: 4 to 3: 4.

(Process for Fabricating Material for Concavo-convex Layer) (S1)
Using the same material as the above-mentioned material for the electrolyte layer, the viscosity, additives, solid content concentration, etc. are appropriately adjusted so that the dispersibility of the material deteriorates when the slurry is produced. Further, resin particles are added in order to form agglomeration of materials such as ScYSZ, YSZ, and GDC. Examples of the resin particles include acrylic resin, polystyrene particles, nylon fine particles, and phenol resin. The size of the resin particles is preferably larger than the particle size of the oxide ion conductive material powder. For example, the particle size of the resin particles is 1.5 times or more that of the oxide ion conductive material powder. Further, in order to increase the aggregation effect, the particle size of the resin particles is more preferably three times or more that of the oxide ion conductive material powder. It is more preferable that the particle size of the resin particles is 5 times or more that of the oxide ion conductive material powder. The particle size of the oxide ion conductive material powder in the material for the uneven layer is preferably smaller than the particle size of the oxide ion conductive material powder in the material for the electrolyte layer. This is because it becomes easy to form irregularities on the surface of the electrolyte layer 40. For example, the D50% particle size of the oxide ion conductive material powder in the material for the uneven layer may be 1/3 or less with respect to the D50% particle size of the oxide ion conductive material powder in the material for the electrolyte layer. It is more preferably 1/5 or less, and even more preferably 1/10 or less.

(Baking step) (S2)
First, a support green sheet is produced by applying a support material on a PET (polyethylene terephthalate) film. A mixed layer green sheet is produced by applying a material for a mixed layer on another PET film. An anode green sheet is produced by applying an anode material on another PET film. An electrolyte layer green sheet is produced by applying a material for an electrolyte layer on another PET film. By applying the material for the uneven layer on another PET film, the uneven layer green sheet is produced. Since the uneven layer green sheet is used as a green sheet to be attached to the surface layer of the electrolyte layer green sheet, it is, for example, a thin sheet of 1 μm or less. For example, a plurality of support green sheets, one mixed layer green sheet, one anode green sheet, one electrolyte layer green sheet, and one uneven layer green sheet are laminated in this order to obtain a predetermined size. It is cut and calcined in a reducing atmosphere having an oxygen partial pressure of 10 to ²⁰ atm or less in a temperature range of about 1100 ° C to 1300 ° C. Thereby, a half cell including the support 10, the mixed layer 20, the electrode skeleton of the anode 30, the electrolyte layer 40, and the uneven layer can be obtained.

(Anode impregnation step) (S3)
Next, the raw materials of the oxide ion conductive ceramics 33 and the catalyst metal 34 are impregnated into the electrode skeleton of the anode 30. For example, water or alcohols (Zr, Y, Sc, Ce, Gd, Ni nitrates or chlorides so that Gd-doped ceria or Sc, Y-doped zirconia and Ni are produced when calcined at a predetermined temperature in a reducing atmosphere. Dissolve in ethanol, 2-propanol, methanol, etc.), impregnate the half cell, dry, and repeat the heat treatment as many times as necessary.

(Intermediate layer forming step) (S4)
The intermediate layer 50 is formed by forming the oxide ion conductive ceramics contained in the intermediate layer 50 on the electrolyte layer 40 by, for example, PVD. For example, the intermediate layer 50 is formed by forming a film of Ce _0.8 Gd _0.2 O _2-x so as to have a thickness of 1 μm by PVD. For example, at the time of film formation, the film formation rate and the substrate heating temperature are controlled so that voids are lined up at predetermined intervals from the electrolyte layer 40 to the cathode 60 in the intermediate layer 50 at predetermined intervals. In this case, the film forming speed is preferably 10 nm / hour to 50 nm / hour, and the substrate heating temperature is preferably 200 ° C. to 600 ° C.

(Cathode forming step) (S5)
Next, the cathode material is applied onto the intermediate layer 50 by screen printing or the like and dried. Then, the cathode material is sintered by heat treatment in an air atmosphere at a temperature of 1000 ° C. or lower to form the cathode 60. In order to suppress the oxidation of the metal, the temperature during the heat treatment is preferably 900 ° C. or lower, more preferably 800 ° C. or lower.

According to the above manufacturing method, in the process of producing the material for the uneven layer, the dispersibility of the material is adjusted so as to be poor, so that the surface of the electrolyte layer 40 after firing is convex with a plurality of recesses 41 on the cathode 60 side. The portions 42 are alternately formed. As a result, the intermediate layer 50 also follows the shape of the surface of the electrolyte layer 40 on the cathode 60 side. Therefore, on the surface of the intermediate layer 50 on the cathode 60 side, the concave portion 51 is formed so as to substantially coincide with the position of the concave portion 41, and the convex portion 52 is formed so as to substantially coincide with the position of the convex portion 42. In the printing method, it is difficult to form the unevenness only in the in-plane one-dimensional direction, but in the manufacturing method according to the present embodiment, the unevenness can be formed in the in-plane two-dimensional direction. Concavities and convexities are also formed on the surface of the intermediate layer 50 on the side of the electrolyte layer 40 along the surface of the electrolyte layer 40 on the side of the cathode 60. Further, on the surface of the cathode 60 on the intermediate layer 50 side, the convex portion 61 is formed at the portion where the concave portion 51 is formed, and the concave portion 62 is formed at the portion where the convex portion 52 is formed.

Further, according to the above manufacturing method, as illustrated in FIG. 9, the green sheet 80 for the uneven layer is laminated on the electrolyte layer green sheet 70. The particle size of the oxide ion conductive material powder 81 contained in the uneven layer green sheet 80 is smaller than the particle size of the oxide ion conductive material powder 71 contained in the electrolyte layer green sheet 70. Further, the green sheet 80 for the uneven layer contains resin particles 82. The resin particles 82 function as spacers, and the oxide ion conductive material powder 81 becomes aggregated. The resin particles 82 are removed in the firing step. The agglomerated plurality of oxide ion conductive material powders 81 become convex portions 42 after firing. As a result, unevenness arranged in the two-dimensional direction is formed in the surface of the electrolyte layer 40 on the intermediate layer 50 side after firing. As a result, the intermediate layer 50 also follows the shape of the surface of the electrolyte layer 40 on the intermediate layer 50 side. Therefore, on the surface of the intermediate layer 50 on the cathode 60 side, the convex portion 52 is formed so as to substantially coincide with the position of the convex portion 42. In the printing method, it is difficult to form the unevenness only in the in-plane one-dimensional direction, but in the above manufacturing method, the unevenness can be formed in the in-plane two-dimensional direction. Concavities and convexities are also formed on the surface of the intermediate layer 50 on the side of the electrolyte layer 40 along the surface of the electrolyte layer 40 on the side of the cathode 60. Further, on the surface of the cathode 60 on the intermediate layer 50 side, irregularities are formed so as to follow the shape of the surface of the intermediate layer 50 on the cathode 60 side.

Further, at the time of film formation, the film formation rate and the substrate heating temperature are controlled so that voids are lined up at predetermined intervals from the electrolyte layer 40 to the cathode 60 in the intermediate layer 50 along a predetermined line. As a result, the plurality of voids 53 are formed in the intermediate layer 50 so as to be arranged at predetermined intervals along a predetermined line from the convex portion 42 of the electrolyte layer 40 toward the cathode 60.

The fuel cell 100 was manufactured according to the above manufacturing method.

(Example 1)
As the material for the support, SUS (stainless steel) powder was used. ScYSZ was used as the ceramic material for the electrolyte layer. A _LaCrO3 system material was used for the electron conductive ceramics as the anode material, and ScYSZ was used for the oxide ion conductive ceramics. GDC was used as the ceramic material for the intermediate layer. LSC was used as the ceramic material for the cathode material. A _LaCrO3 system material was used as the ceramic material for the mixed layer. SUS was used as the metal material for the mixed layer material. A mixed layer green sheet, an anode green sheet, an electrolyte layer green sheet, and a green sheet for an uneven layer are laminated on the support green sheet, cut to a predetermined size, and the oxygen partial pressure is reduced to ^10-16 atm or less. It was fired in an atmosphere. After impregnating the electrode skeleton of the anode with GDC and Ni, it was calcined at a temperature of 850 ° C. or lower in an atmospheric atmosphere. Then, an intermediate layer of Ce _0.8 Gd _0.2 O _2-x is formed by PVD, and a cathode material is applied onto the intermediate layer by screen printing or the like and dried. Then, the cathode material was sintered by heat treatment in an air atmosphere at a temperature of 1000 ° C. or lower to form a cathode. In Example 1, the dimension a was 120 nm, the dimension a'was 150 nm, the dimension b was 1 μm, the dimension b'was 1 μm, and the dimension c was 500 nm.

(Example 2)
In Example 2, NiO / YSZ was used as the material for the support. Other production conditions were the same as in Example 1. In Example 2, the dimension a was 120 m, the dimension a'was 150 nm, the dimension b was 1 μm, the dimension b'was 1 μm, and the dimension c was 500 nm.

(Example 3)
In Example 3, the conditions for producing the concavo-convex sheet were changed to reduce the size of the concavo-convex. Other production conditions were the same as in Example 1. In Example 3, the dimension a was 50 nm, the dimension a'was 80 nm, the dimension b was 1 μm, the dimension b'was 1 μm, and the dimension c was 500 nm.

(Comparative Example 1)
In Comparative Example 1, the green sheet for the uneven layer was not provided. Other conditions were the same as in Example 1. In Comparative Example 1, since the green sheet for the uneven layer was not provided, the unevenness did not appear on the surface of the electrolyte layer layer on the cathode side, and the unevenness did not appear on the intermediate layer and the cathode. The dimension c was 500 nm.

(Comparative Example 2)
In Comparative Example 2, the treatment time of PVD was tripled as that of Example 1, and the thickness of the intermediate layer was tripled (about 1.5 μm). Other conditions were the same as in Example 1. The dimension c was 1.5 μm.

(Power generation evaluation)
By measuring the impedance of the fuel cells of Examples 1 to 3 and Comparative Examples 1 and 2, each resistance value was separated, and the ohm resistance of the entire fuel cell and the reaction resistance of the cathode were measured. The results are shown in Table 1. As shown in Table 1, in Example 1, the ohmic resistance was 0.25 Ω · cm ² . In Example 2, the ohmic resistance was 0.30 Ω · cm ² . In Example 3, the ohmic resistance was 0.25 Ω · cm ² . As described above, in Examples 1 to 3, the ohmic resistance was low. It is considered that this is because the unevenness on both sides of the intermediate layer makes the resistance during ion conduction almost the same as that without the uneven structure (Comparative Example 1). The reason why the ohmic resistance of Examples 1 and 3 was lower than that of Example 2 is considered to be that a metal support having high electron conductivity was used. In Comparative Example 1, the ohmic resistance was 0.25 Ω · cm ² . It is considered that the ohm resistance in Comparative Example 1 is about the same as that in Example 1 because the ohm resistance depends only on the thickness (dimension c) of the intermediate layer. On the other hand, in Comparative Example 2, the ohmic resistance was larger than that in Example 1 and Comparative Example 1, and was 0.34 Ω · cm ² . It is considered that this is because the ohmic resistance increased due to the thickening of the intermediate layer.

In Example 1, the reaction resistance at the cathode was 0.27 Ω · cm ² . In Example 2, the reaction resistance at the cathode was 0.27 Ω · cm ² . In Example 3, the reaction resistance at the cathode was 0.31 Ω · cm ² . As described above, in Examples 1 to 3, the reaction resistance at the cathode was low. It is considered that this is because the unevenness is formed two-dimensionally on the surface of the intermediate layer on the cathode side in a plan view, so that the contact area between the intermediate layer and the cathode is increased. It is considered that the reaction resistance of Examples 1 and 2 was lower than that of Example 3 because the dimension a and the dimension a'were large and the unevenness became large. On the other hand, in Comparative Example 1, the reaction resistance at the cathode was 0.56 Ω · cm ² , and in Comparative Example 2, the reaction resistance at the cathode was 0.52 Ω · cm ² , which were significantly higher. It is considered that this is because the contact area between the intermediate layer and the cathode was not sufficiently large because the unevenness was not formed in the intermediate layer.

(Example 4)
As the material for the support, SUS (stainless steel) powder was used. ScYSZ was used as the ceramic material for the electrolyte layer. Acrylic resin, polystyrene particles, nylon fine particles, phenol resin and the like were added as resin particles to the material for the uneven layer. A _LaCrO3 system material was used for the electron conductive ceramics as the anode material, and ScYSZ was used for the oxide ion conductive ceramics. GDC was used as the ceramic material for the intermediate layer. LSC was used as the ceramic material for the cathode material. A _LaCrO3 system material was used as the ceramic material for the mixed layer. SUS was used as the metal material for the mixed layer material. A mixed layer green sheet, an anode green sheet, an electrolyte layer green sheet, and a green sheet for an uneven layer are laminated on the support green sheet, cut to a predetermined size, and the oxygen partial pressure is reduced to ^10-16 atm or less. It was fired in an atmosphere. After impregnating the electrode skeleton of the anode with GDC and Ni, it was calcined at a temperature of 850 ° C. or lower in an atmospheric atmosphere. Then, an intermediate layer of Ce _0.8 Gd _0.2 O _2-x was formed by PVD, and a cathode material was applied onto the intermediate layer by screen printing or the like and dried. Then, the cathode material was sintered by heat treatment in an air atmosphere at a temperature of 1000 ° C. or lower to form a cathode. The film forming rate when forming the intermediate layer was 10 nm / hour, and the substrate heating temperature was 300 ° C. When the STEM (scanning transmission electron microscope) photograph of the intermediate layer was confirmed, it was confirmed that a plurality of voids were formed in the intermediate layer from the electrolyte layer to the cathode at intervals along a predetermined line. The average diameter of the voids was 10 nm. The average number of voids 53 per convex portion 52 from the electrolyte layer to the cathode was 500.

(Example 5)
In Example 5, NiO / YSZ was used as the support material. Other production conditions were the same as in Example 4. In Example 5, the film forming rate when forming the intermediate layer was 10 nm / hour, and the substrate heating temperature was 300 ° C. When the STEM photograph of the intermediate layer was confirmed, it was confirmed that a plurality of voids were formed in the intermediate layer from the electrolyte layer to the cathode at intervals along a predetermined line. The average diameter of the voids was 10 nm. The average number of voids per convex portion 52 from the electrolyte layer to the cathode was 500.

(Comparative Example 3)
In Comparative Example 3, the green sheet for the uneven layer was not provided. Other conditions were the same as in Example 4. In Comparative Example 3, since the green sheet for the uneven layer was not provided, the unevenness did not appear on the surface of the electrolyte layer layer on the cathode side, and the unevenness did not appear on the intermediate layer and the cathode.

(Comparative Example 4)
In Comparative Example 4, a green sheet for the uneven layer was provided, and in the PVD treatment of the intermediate layer, the film formation rate was 10 nm / hour, and the substrate heating temperature was 600 ° C. Other conditions were the same as in Example 4. Since the substrate heating temperature was high, no void 53 was observed when observing the cross section. It was confirmed that all the uneven parts were dense.

(Power generation evaluation)
By measuring the impedance of the fuel cells of Examples 4 and 5 and Comparative Examples 3 and 4, each resistance value was separated, and the ohm resistance of the entire fuel cell and the reaction resistance of the cathode were measured. The results are shown in Table 2. As shown in Table 2, in Example 4, the ohmic resistance was 0.25 Ω · cm ² . Further, in Example 5, the ohmic resistance was 0.30 Ω · cm ² . Thus, in Examples 4 and 5, the ohmic resistance was low. It is considered that this is because the unevenness on both sides of the intermediate layer makes the resistance at the time of ion conduction almost the same as that without the uneven structure (comparative example). It is considered that the reason why the ohmic resistance of Example 4 was lower than that of Example 5 was that a metal support having high electron conductivity was used.

In Example 4, the reaction resistance at the cathode was 0.27 Ω · cm ² . In Example 5, the reaction resistance at the cathode was 0.27 Ω · cm ² . In Comparative Example 4, the reaction resistance at the cathode was 0.27 Ω · cm ² . As described above, in Example 4, Example 5, and Comparative Example 4, the reaction resistance at the cathode was low. It is considered that this is because the contact area between the intermediate layer and the cathode has increased due to the formation of irregularities on the surface of the intermediate layer on the cathode side. On the other hand, in Comparative Example 3, the reaction at the cathode was 0.56 Ω · cm ² , which was significantly higher. It is considered that this is because the contact area between the intermediate layer and the cathode was not sufficiently large because the unevenness was not formed in the intermediate layer.

Next, for the fuel cells of Examples 4 and 5 and Comparative Examples 3 and 4, after 5000 cycles of temperature rise and fall, impedance measurement was performed again, each resistance value was separated, and the ohm resistance and cathode of the entire fuel cell were obtained. Reaction resistance was measured. In one cycle, the temperature was raised to 750 ° C. and lowered to room temperature. The results are shown in Table 3.

As shown in Table 3, in Example 4, the ohmic resistance was 0.25 Ω · cm ² , and the reaction resistance of the cathode was 0.30 Ω · cm ² . In Example 5, the ohmic resistance was 0.30 Ω · cm ² and the reaction resistance of the cathode was 0.31 Ω · cm ² . Thus, the ohmic resistance and the reaction resistance of the cathode did not change much before and after the temperature rise and fall. It is considered that this is because the peeling did not occur between the electrolyte layer and the intermediate layer. After that, the cell surface was visually confirmed, but no peeling of the intermediate layer was observed. In Comparative Example 3, the ohmic resistance was 0.40 Ω · cm ² and the reaction resistance of the cathode was 0.71 Ω · cm ² . In this way, the ohmic resistance has increased significantly. It is considered that this is because the peeling occurred between the electrolyte layer and the intermediate layer due to the difference in the thermal expansion rate between the electrolyte layer and the intermediate layer. After that, when the cell surface was visually inspected, peeling was confirmed in the intermediate layer. In Comparative Example 4, the electromotive force OCV was not confirmed after the temperature was raised and lowered by 5000 cycles, and when the cell was taken out and confirmed, it was confirmed that the intermediate layer was peeled off and the battery could not be operated. Since there are no voids, it is considered that the intermediate layer was peeled off due to thermal expansion.

Although the examples of the present invention have been described in detail above, the present invention is not limited to the specific examples thereof, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

Claims

An electrolyte layer containing a solid oxide having oxide ion conductivity and
An intermediate layer provided on the electrolyte layer and having oxide ion conductivity,
With a cathode provided on the intermediate layer,
The intermediate layer is provided with a plurality of irregularities on the surface on the cathode side so as to be arranged in a two-dimensional direction in a plan view.
The solid oxide fuel cell is characterized in that the intermediate layer is provided with a plurality of irregularities on the surface on the electrolyte layer side along the plurality of irregularities on the surface on the cathode side.
The solid oxide fuel cell according to claim 1, wherein the unevenness on the surface of the intermediate layer on the cathode side is formed in the form of particles.
The solid oxide according to claim 1 or 2, wherein the vertical distance a between the peak and the valley is 0.05 μm or more and 3 μm or less in the unevenness of the surface of the intermediate layer on the cathode side. Type fuel cell.
The aspect according to any one of claims 1 to 3, wherein the horizontal distance b between the peaks is 0.1 μm or more and 5 μm or less in the unevenness of the surface of the intermediate layer on the cathode side. The solid oxide fuel cell described.
In the unevenness of the surface of the intermediate layer on the cathode side, a / b, which is the ratio of the vertical distance a between the peaks and valleys and the horizontal distance b between the peaks and peaks, is 1/10 or more and 20/1 or less. The solid oxide fuel cell according to any one of claims 1 to 4, wherein the fuel cell is characterized by being present.
Claims 1 to 5 are characterized in that a plurality of irregularities are provided on the surface of the electrolyte layer on the side of the intermediate layer so as to follow the irregularities on the surface of the intermediate layer on the side of the electrolyte layer. The solid oxide fuel cell according to any one of the above.
The solid oxide fuel cell according to claim 6, wherein the vertical distance a'between the peaks and valleys is 0.05 μm or more and 3 μm or less in the unevenness of the surface of the electrolyte layer on the intermediate layer side. battery.
The solid according to claim 6 or 7, wherein the horizontal distance b'between the peaks is 0.1 μm or more and 5 μm or less in the unevenness of the surface of the electrolyte layer on the intermediate layer side. Oxide fuel cell.
In the unevenness of the surface of the electrolyte layer on the intermediate layer side, a'/ b', which is the ratio of the vertical distance a'between the peaks and the valley and the horizontal distance b'between the peaks and the peaks, is 1/10 or more. The solid oxide fuel cell according to any one of claims 6 to 8, wherein the fuel cell is 20/1 or less.
Along the vertical distance a between the peaks and valleys on the unevenness of the surface on the cathode side of the intermediate layer and the unevenness on the surface of the intermediate layer on the side of the intermediate layer of the intermediate layer. One of claims 1 to 9, wherein the vertical distance a'between the peaks and valleys in the plurality of provided irregularities has a relationship of 0.5≤a / a'≤1. The solid oxide fuel cell described in.
Along the horizontal distance b between the peaks on the unevenness of the surface on the cathode side of the intermediate layer and the unevenness on the surface of the intermediate layer on the side of the intermediate layer. One of claims 1 to 10, wherein the horizontal distance b'between the peaks in the plurality of provided irregularities has a relationship of 0.5≤b / b'≤1. The solid oxide fuel cell described in.
The mountain in the unevenness of the surface on the cathode side of the intermediate layer and the mountain in the unevenness provided along the unevenness on the surface of the intermediate layer on the side of the electrolyte layer in the surface of the electrolyte layer on the intermediate layer side. The solid oxide fuel cell according to any one of claims 1 to 10, wherein the vertical distance from the mountain corresponding to the above is 10 nm or more and 3 μm or less.
An electrolyte layer containing a solid oxide having oxide ion conductivity and
An intermediate layer provided on the electrolyte layer and having oxide ion conductivity,
With a cathode provided on the intermediate layer,
The intermediate layer is formed along the unevenness provided on the surface of the electrolyte layer on the intermediate layer side.
A solid oxide fuel cell characterized in that, in the intermediate layer, a plurality of voids are formed so as to be arranged at intervals along a predetermined line from the electrolyte layer side to the cathode side.
The solid oxide fuel cell according to claim 13, wherein in the intermediate layer, the number density of the voids in the convex portion with respect to the cathode side is larger than the number density of the voids in the concave portion with respect to the cathode side. ..
The solid oxide fuel cell according to claim 13 or 14, wherein the average diameter of the voids is 50 nm or less.
The aspect according to any one of claims 13 to 15, wherein the unevenness of the electrolyte layer is provided so as to be arranged in a two-dimensional direction in a plan view on the surface on the intermediate layer side. Solid oxide fuel cell.
The solid oxide fuel cell according to any one of claims 13 to 16, wherein the intermediate layer is a material to which an additive is added to ceria.
An electrolyte layer green sheet is prepared by applying a slurry containing oxide ion conductive material powder.
The electrolyte layer green sheet contains an oxide ion conductive material powder having a D50% particle size smaller than the D50% particle size of the oxide ion conductive material powder of the electrolyte layer green sheet, and resin particles. The process of forming an electrolyte layer with irregularities on the surface by applying a slurry and firing it,
An intermediate layer having oxide ion conductivity and not cathode activity was formed on the electrolyte layer by the PVD method.
A cathode is formed on the intermediate layer to form a cathode.
When the intermediate layer is formed by the PVD method, the film forming speed and the substrate are formed so that a plurality of voids are arranged at intervals along a predetermined line from the electrolyte layer side to the cathode side. A method for manufacturing a solid oxide fuel cell, which comprises controlling at least one of the heating temperatures.