WO2017002264A1

WO2017002264A1 - Solid oxide fuel cell and method for manufacturing same

Info

Publication number: WO2017002264A1
Application number: PCT/JP2015/069152
Authority: WO
Inventors: 矢島　健太郎; 隆夫和泉
Original assignee: 日産自動車株式会社
Priority date: 2015-07-02
Filing date: 2015-07-02
Publication date: 2017-01-05

Abstract

A solid oxide fuel cell (1) is provided with a fuel electrode (12) and an air electrode (11), as well as a solid electrolyte layer (13) sandwiched between the fuel electrode and the air electrode. The solid oxide fuel cell is further provided with a current collector (14) placed on the air-electrode side and a current-collecting material part (20) that is disposed between the air electrode and the current collector and that has a protrusion (23) formed on a surface on the air-electrode side. Then, a thin metal layer (24) on which is formed a plastic region that has a smaller yield stress than the current-collecting material part and the air electrode and that has been subjected to plastic deformation is provided between the air electrode and the protrusion of the current-collecting material part.

Description

Solid oxide fuel cell and method for producing the same

The present invention relates to a solid oxide fuel cell and a method for manufacturing the same. More specifically, the present invention relates to a solid oxide fuel cell with reduced current collecting resistance between an air electrode and a current collector and a method for producing the solid oxide fuel cell.

In recent years, the use of various fuel cells for automobiles has been studied due to the growing interest in global environmental issues. A fuel cell is a device that converts chemical energy into electrical energy through an electrochemical reaction. Among the various fuel cells, the solid oxide fuel cell (SOFC) has high efficiency and has attracted attention as a power source for automobiles.

A solid oxide fuel cell (SOFC) has a three-layer structure in which a fuel electrode, a solid electrolyte layer, and an air electrode are stacked, and this is used as a power generation unit of the fuel cell. A fuel gas such as hydrogen or hydrocarbon is supplied to the fuel electrode, and an oxidant gas such as air is supplied to the air electrode to generate electricity. In addition, current collectors (separators) are arranged on the air electrode and the fuel electrode, respectively.

As such a solid oxide fuel cell, conventionally, a flat unit cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and a separator are alternately stacked, and a separator and a fuel electrode A flat-type solid electrolyte fuel cell having a heat-resistant wire mesh sandwiched therebetween is disclosed (for example, see Patent Document 1). It is also disclosed that the wire mesh is made of nickel. With such a configuration, the fuel electrode and the wire mesh are in close contact with each other, thereby increasing the current collection efficiency.

JP-A-8-45516

However, when the nickel wire net in Patent Document 1 is used at the air electrode, nickel easily oxidizes at a high temperature, resulting in a problem that current collecting resistance increases.

The present invention has been made in view of such problems of the conventional technology. And the objective of this invention is providing the manufacturing method of the solid oxide fuel cell which can reduce the current collection resistance between an electrode and a collector, and the said solid oxide fuel cell. is there.

In order to solve the above problems, a solid oxide fuel cell according to an aspect of the present invention includes a current collector and an air electrode. Further, the fuel cell includes a current collector member that exists between the air electrode and the current collector and has a convex portion formed on the surface on the air electrode side. And between the air electrode and the convex part of the current collector part, a thin metal layer having a yield stress smaller than that of the current collector part and having a plastically deformed plastic region is provided.

The metal thin layer is plastically deformed by providing a metal having a low yield stress as a metal thin layer between the convex portion of the current collector and the air electrode. Therefore, even if the pressing load between the current collector part and the air electrode is not excessively increased, the contact rate between them is improved, so that the current collecting resistance can be reduced.

FIG. 1 is a perspective view showing an exploded state of a solid oxide fuel cell according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a cross section of the air electrode current collector, the current collector part, the metal thin layer, and the air electrode in the solid oxide fuel cell shown in FIG. FIG. 3 shows the effect of reducing current collection resistance by a structure having a convex portion on the surface. (A) shows a method for measuring electrical resistance between hastelloy rods, and (b) shows a rod in the case where the hastelloy rods are brought into direct contact with each other and a platinum mesh is interposed between the rods. It is a graph which shows the relationship between the surface pressure in between and current collection resistance. FIG. 4A is a schematic diagram showing a state of deformation of the structure at the interface between the rod and the structure when a pressing load is applied to the nickel-based alloy structure. FIG. 4B is a schematic view showing a state of deformation of the structure at the interface between the rod and the structure when a pressing load is applied to the platinum structure. FIG. 5 is a graph showing the relationship between the pressing load on the mesh and the contact area between the rod and the mesh in a mesh made of platinum and a mesh made of a nickel-based alloy. FIG. 6 is a graph showing the relationship between the total contact area between the rod and the mesh in the mesh made of platinum and the mesh made of nickel-based alloy and the area of the contact surface of the plastic region in the mesh. FIG. 7 is a schematic cross-sectional view showing a state of deformation of the metal thin layer and the current collector part at the interface between the electrode and the current collector part when a pressing load is applied to the current collector part and the metal thin layer according to the present embodiment. FIG. FIG. 8 is a schematic cross-sectional view showing an arrangement example of the metal thin layer with respect to the current collector portion. FIG. 9 is a schematic diagram illustrating an example of a cross-sectional shape of the current collector portion. FIG. 10 is a schematic diagram for explaining a manufacturing process of the solid oxide fuel cell of Example 1. FIG. 11 is a schematic diagram for explaining a production process of the solid oxide fuel cell of Example 2. FIG. 12 is a schematic diagram for explaining a manufacturing process of the solid oxide fuel cell of Example 3. FIG. 13 is a schematic diagram for explaining a method for evaluating the solid oxide fuel cells of Example 1 and Comparative Example. FIG. 14 is a graph showing measurement results of current collection resistance in the solid oxide fuel cells of Example 1 and Comparative Example.

Hereinafter, a solid oxide fuel cell and a manufacturing method thereof according to an embodiment of the present invention will be described in detail. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

[Solid oxide fuel cell]
As shown in FIG. 1, the solid oxide fuel cell 1 according to this embodiment includes a single electrode including an air electrode 11 and a fuel electrode 12, and a solid electrolyte layer 13 sandwiched between the air electrode 11 and the fuel electrode 12. It has a cell 10. The single cell 10 is sandwiched between the air electrode current collector 14 and the fuel electrode current collector 15.

As shown in FIG. 1, the air electrode current collector 14 includes a plurality of oxidant gas channels 14a, and the fuel electrode current collector 15 includes a plurality of fuel gas channels 15a. The oxidant gas flow path 14a and the fuel gas flow path 15a are a large number of linear flow paths (parallel flow paths) arranged in parallel to each other. The cross-sectional shapes of the flow paths (oxidant gas flow path 14a, fuel gas flow path 15a) provided in the fuel electrode current collector 15 and the air electrode current collector 14 are convex portions called ribs, and concave portions called channels. Consists of. Among these, the rib of the air electrode current collector 14 is electrically connected to the air electrode 11, whereby electrons are conducted between the air electrode current collector 14 and the air electrode 11. Further, when the rib of the fuel electrode current collector 15 is electrically connected to the fuel electrode 12, electrons are conducted between the fuel electrode current collector 15 and the fuel electrode 12.

The solid oxide fuel cell 1 includes a current collector 20 between the air electrode 11 and the air electrode current collector 14 as shown in FIGS. 1 and 2. As will be described later, the current collector member 20 is composed of a structure in which convex portions 23 are formed on a surface such as a metal mesh. By providing such a current collector member 20, it is possible to suppress the current collection resistance between the air electrode 11 and the air electrode current collector 14.

More specifically, a pressing load is usually applied to a contact portion between the current collector (the air electrode current collector 14 and the fuel electrode current collector 15) and the air electrode 11 and the fuel electrode 12 in order to ensure electrical connection. Is added. Further, it is generally known that increasing the pressing load increases the contact interface between the current collector and the electrode and reduces the current collection resistance (ASR). However, in order to increase the pressing load of the current collector and the electrode, it is necessary to employ a large-diameter bolt for increasing the surface pressure during assembly. Therefore, the weight of the fuel cell stack increases due to the increase in the weight of the bolt, and the output per unit volume decreases due to the increase in the volume of the bolt. Therefore, it is necessary to reduce the current collection resistance between the current collector and the electrode without increasing the pressing load on the current collector and the electrode.

As a result of intensive studies by the inventor, as a method of reducing the current collecting resistance without increasing the pressing load, the current collecting resistance is reduced by using a structure having a convex portion on the surface, such as a mesh. I found that it was effective. FIG. 3 shows the effect of reducing current collection resistance by a structure having a convex portion on the surface. Specifically, as shown in FIG. 3A, the current and voltage between the rods when the surface pressure between the rods is increased by using a rod made of Hastelloy (registered trademark) which is a nickel-based alloy. Measured and the change in current collecting resistance was measured. At this time, the change in current collecting resistance was measured with and without a platinum mesh between the rods. FIG. 3B shows the relationship between the surface pressure between the rods and the current collecting resistance when the Hastelloy rods are in direct contact with each other and a platinum mesh is interposed between the rods. As shown in FIG.3 (b), it turns out that current collection resistance falls as the surface pressure between rods increases. And when a platinum mesh is interposed, it turns out that current collection resistance falls compared with the case where a platinum mesh is not interposed.

However, the effect of reducing the current collecting resistance between the rods varies greatly depending on the material of the structure having the convex portions on the surface. In other words, such an effect of reducing the current collecting resistance is caused by a contact surface in the plastic region being formed on the convex portion of the structure at the contact surface between the rod and the structure provided with the convex portion on the surface. For example, Hastelloy, which is a nickel-based alloy, has a high yield stress, which is a stress in the vicinity of transition from elastic deformation to plastic deformation. Therefore, when a structure (mesh) made of Hastelloy is used, even if the pressing load on the structure is increased, as shown in FIG. 4A, at the contact interface between the rod and the convex portion 23 of the structure. A large number of elastic contact surfaces 21 formed by elastic deformation of the convex portions 23 of the structure are generated. When the pressing load is further increased, a plastic contact surface 22 formed by plastic deformation of the convex portion 23 of the structure is generated, but even in that case, the elastic contact surface 21 is dominant.

In contrast, platinum has a low yield stress. Therefore, in the case of using a structure (mesh) made of platinum, by increasing the pressing load on the structure, as shown in FIG. 4B, the structure is formed at the contact interface between the rod and the convex portion 23 of the structure. Many contact surfaces 22 in the plastic region formed by plastic deformation of the convex portions 23 of the body are generated. Thus, when the yield stress of the material which comprises a structure differs, even if the load concerning a structure is the same, the area of the plastic zone produced | generated in the contact surface of the convex part 23 of the surface of a rod and a structure differs. . And when there are many contact surfaces 21 of an elastic region, in order to raise the contact area between the convex part 23 of a structure and a rod, it is necessary to maintain a state with a high pressing load. On the other hand, when there are many contact surfaces 22 in the plastic region, since the convex portion 23 of the structure is plastically deformed, the contact between the convex portion 23 of the structural body and the rod can be achieved without increasing the pressing load. The area can be kept high.

FIG. 5 shows the relationship between the pressing load on the mesh and the contact area between the rod and the mesh in the mesh made of platinum and the mesh made of nickel-based alloy (Hastelloy). In FIG. 5, symbol A relates to all contact surfaces of the platinum mesh, symbol B relates to the contact surface of the plastic region of the platinum mesh, symbol C relates to all the contact surfaces of the nickel base alloy mesh, and symbol D denotes the nickel base alloy. It relates to the contact surface of the plastic region of the mesh.

As shown in FIG. 5, in the case of a platinum mesh, it can be seen that as the pressing load increases, the area of all the contact surfaces of the platinum mesh and the contact surface of the plastic region increases. On the other hand, in the case of the nickel-based alloy mesh, as the pressing load increases, the area of the entire contact surface of the nickel-based alloy mesh increases, but the contact surface of the plastic region does not increase greatly. Therefore, when using a nickel base alloy mesh, in order to maintain a high contact area, it turns out that it is necessary to maintain a pressing load in a high state.

FIG. 6 shows the relationship between the total contact area between the rod and the mesh in the mesh made of platinum and the mesh made of nickel-based alloy (Hastelloy) and the area of the contact surface of the plastic region in the mesh. In FIG. 6, symbol E relates to a platinum mesh, and symbol F relates to a nickel-based alloy mesh.

As shown in FIG. 6, as the pressing load increases, the area of all contact surfaces of both the platinum mesh and the nickel-based alloy mesh increases. However, as the pressing load increases, the contact area of the plastic region in the platinum mesh increases, but the contact surface of the plastic region in the nickel-based alloy mesh does not increase greatly. This also shows that by using a platinum mesh, the contact surface of a plastic region increases with a low pressing load, and as a result, a high contact area can be maintained.

The solid oxide fuel cell 1 of the present embodiment is an application of the effect that the current collection resistance is reduced without increasing the pressing load by increasing the contact surface in such a plastic region. In the present specification, such an effect is referred to as “current collection resistance reduction effect in a plastic region”.

Here, Table 1 shows Young's modulus and yield stress of platinum, nickel, nickel-based alloy (Hastelloy) and ferritic stainless steel (Crofer22APU). For example, by using platinum or nickel, which has a low yield stress, as the material of the structure with convex portions on the surface, the current collection resistance between the current collector and the electrode can be reduced due to the current collection resistance reduction effect in the plastic region. It is estimated that it can be reduced. However, platinum is very expensive and the cost is greatly increased. Moreover, since nickel is easily oxidized at a high temperature on the air electrode side, the current collection resistance increases as a result. On the other hand, nickel base alloys such as Hastelloy and stainless steels such as Crofer 22APU have high oxidation resistance but high yield stress, and therefore it is difficult to obtain the current collecting resistance reduction effect in the plastic region.

Therefore, in this embodiment, as shown in FIG.2 and FIG.7, the metal thin layer 24 which consists of a material whose yield stress is smaller than the current collection material part 20 and the air electrode 11 on the surface of the current collection material part 20 at the air electrode side. Is provided. By providing such a thin metal layer 24, a plastic contact surface 22 is formed by the thin metal layer 24 between the current collector 20 and the air electrode 11. Since the metal thin layer 24 has a lower yield stress than the current collector 20 and the air electrode 11, the plastic contact area 22 is generated more than the elastic contact area 21. Therefore, the current collection resistance between the current collector member 20 and the air electrode 11 can be reduced without increasing the pressing load due to the effect of reducing the current collection resistance in the plastic region.

Note that, as shown in FIG. 7, by increasing the pressing load of the current collector member 20, an elastic region 25 and a plastic region 26 are also generated in the convex portion 23 on the surface of the current collector member 20. However, the current collector 20 is preferably made of an oxidation-resistant metal as will be described later, and many of such oxidation-resistant metals have a high yield stress. Therefore, in the current collector member 20, more elastic region 25 is generated than plastic region 26. However, in the present embodiment, since the contact surface 22 in the plastic region is generated by providing the metal thin layer 24, the current collection resistance reduction effect in the plastic region can be achieved without increasing the pressing load of the current collector member 20. Can be obtained.

The thickness t1 of the thin metal layer 24 is preferably 0.01 μm or more. That is, as shown in FIG. 7, it is preferable that the thickness t1 of the thin metal layer 24 after the current collector member 20 provided with the thin metal layer 24 is pressed against the air electrode 11 is 0.01 μm or more. When the thickness t1 of the metal thin layer 24 is 0.01 μm or more, a large number of contact surfaces 22 in the plastic region are generated, and it becomes possible to further enhance the current collection resistance reduction effect in the plastic region. In addition, the metal thin layer 24 can be made thinner to reduce the material cost. The upper limit of the thickness t1 of the thin metal layer 24 is not particularly limited, but can be, for example, 100 μm or less. The thickness t1 of the thin metal layer 24 can be obtained by observing the cross section of the thin metal layer 24 with a scanning electron microscope (SEM).

The material constituting the metal thin layer 24 is not particularly limited as long as it has a lower yield stress than the current collector 20 and the air electrode 11. However, the metal thin layer 24 is preferably made of at least one selected from the group consisting of silver, platinum and gold. Alternatively, the thin metal layer 24 is preferably made of an alloy containing at least one of silver, platinum and gold and at least one of palladium, ruthenium and cobalt. Since these materials have low yield stress and excellent oxidation resistance at high temperatures, it is possible to reduce electrical resistance even when used on the air electrode side.

The current collector member 20 is preferably made of an oxidation resistant metal. Therefore, the current collector member 20 is preferably made of an alloy containing at least one of chromium and iron as a main component. That is, it is preferable to use an alloy containing 50 mass% or more of at least one of chromium and iron for the current collector part 20. By using such an alloy as the current collector 20, it becomes possible to eliminate the influence of oxidation of the current collector 20 and suppress an increase in current collection resistance.

Specifically, at least one of stainless steel and a chromium-based alloy can be used as the alloy constituting the current collector portion 20. Examples of the stainless steel include ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. Examples of ferritic stainless steel include SUS430, SUS434, and SUS405. Examples of martensitic stainless steel include SUS403, SUS410, and SUS431. Examples of austenitic stainless steel include SUS201, SUS301, and SUS305. Examples of the chromium-based alloy include Ducrloy CRF (94Cr5Fe1Y ₂ O ₃ ), Crofer 22 alloy, and ZMG232L.

The current collector 20 is also preferably made of an alloy containing nickel as a main component. That is, it is also preferable to use a nickel-based alloy containing 50 mass% or more of nickel for the current collector member 20. Examples of the nickel-based alloy include Inconel (registered trademark) and Hastelloy (registered trademark).

As the current collector member 20, it is preferable to use a structure having a convex portion 23 formed on the surface, for example, a structure such as a mesh (metal mesh). That is, the current collector part 20 may be a structure formed by assembling wires made of the above materials, or may be a structure formed by knitting the wires. The method for knitting the wire is not particularly limited, and for example, methods such as plain weaving, twill weaving, and tatami weaving can be employed. Moreover, the convex part 23 formed in the surface of the current collection material part 20 can be formed in dotted line shape, linear form, a grid | lattice form, and mesh shape, for example. Further, the current collector member 20 may be integrated with the air electrode current collector 14.

As shown in FIG. 7, the thin metal layer 24 only needs to be interposed at least between the electrically conductive surfaces of the air electrode 11 and the air electrode current collector 14. Therefore, as shown in FIG. 8A, the metal thin layer 24 is provided on the entire surface of the air electrode 11, and the convex portion 23 formed on the surface of the current collector 20 is brought into contact with the metal thin layer 24. be able to. Moreover, as shown in FIG.8 (b), it can be set as the structure which provides the metal thin layer 24 only in the surface where the current collection material part 20 and the air electrode 11 oppose. Furthermore, as shown in FIG. 8C, the air electrode 11 and the air electrode current collector 14 can be brought into contact with each other after the metal thin layer 24 is provided over the entire circumference of the current collector member 20. . Further, as shown in FIG. 8D, the thin metal layer 24 can be provided only on the surface where the current collector 20 and the air electrode 11 face each other and the periphery thereof. However, since the metal thin layer 24 only needs to be interposed between the air electrode 11 and the air electrode current collector 14, from the viewpoint of reducing the cost by reducing the number of metals constituting the metal thin layer 24, FIG. The configuration shown in FIG. 8B and FIG. 8D is more preferable.

When the current collector 20 is made of a wire, the cross-sectional shape of the wire is not particularly limited. That is, as shown in FIGS. 7 and 8, the current collector member 20 has a substantially circular cross-sectional shape along the stacking direction Y of the air electrode 11, the current collector member 20, and the air electrode current collector 14. it can. However, as shown in FIG. 9, the current collector member 20 has a triangular, semicircular or trapezoidal cross-sectional shape along the stacking direction Y of the air electrode 11, the current collector member 20 and the air electrode current collector 14. Preferably there is. Moreover, it is preferable that the current collector part 20 has a cross-sectional area (XZ plane) perpendicular to the stacking direction Y that decreases from the air electrode current collector 14 toward the air electrode 11. Since the cross section of the current collector 20 is triangular, semicircular or trapezoidal, when a pressing load is applied to the current collector 20, the tip of the current collector 20 (the convex portion 23 on the surface) is crushed. Thus, the area of the surface facing the air electrode 11 increases. Therefore, the conductivity between the current collector 20 and the air electrode 11 can be increased via the thin metal layer 24. The current collector portion may have an elliptical cross-sectional shape along the stacking direction Y.

As described above, the solid oxide fuel cell 1 is provided with the air electrode current collector 14 and the fuel electrode current collector 15 that are electrically connected to the air electrode 11 and the fuel electrode 12, respectively. The current collectors (air electrode current collector 14 and fuel electrode current collector 15) function as a separator that separates the current collecting function from the electrodes (air electrode 11 and fuel electrode 12) from the oxidant gas and the fuel gas. It has the function of. In this specification, it is assumed that the current collector member 20 cannot be distinguished from those that are separate from the current collector and those that are part of the structure of the current collector.

The materials constituting the air electrode current collector 14 and the fuel electrode current collector 15 are not particularly limited. For example, an alloy material having excellent oxidation resistance and conductivity can be used. Specifically, ferritic stainless steel, Inconel, Hastelloy, or the like can be used.

Here, the flow of the oxidant gas flowing through the oxidant gas flow path 14a and the flow of the fuel gas flowing through the fuel gas flow path 15a are orthogonal flows in which the fuel gas and the oxidant gas flow in directions orthogonal to each other within the plane of the single cell 10. (Cross flow). In addition, the flow of the fuel gas and the oxidant gas may be a counter flow that flows in the plane of the single cell 10 and flows in the same direction in the plane of the single cell 10 (coflow). ). Further, the flow of the fuel gas and the oxidant gas may be a return flow that changes the direction of the reaction gas entering from the inlet in the plane of the single cell 10 and flows in the reverse direction. Serpentine flow may be used in which the flow direction of the reaction gas is changed several times in the opposite direction.

As the air electrode 11, one that is strong in an oxidizing atmosphere, permeates the oxidant gas, has high electrical conductivity, and has a catalytic action for converting oxygen molecules into oxide ions can be suitably used. The air electrode 11 may be made of an electrode catalyst or a cermet of an electrode catalyst and an electrolyte material. For example, a metal such as silver (Ag) or platinum (Pt) may be used as the electrode catalyst, but lanthanum strontium cobaltite (La _1-x Sr _x CoO ₃ : LSC) or lanthanum strontium cobalt ferrite ( _{_{_{_{La 1-x Sr x Co 1}}}} -y Fe y O 3: LSCF), samarium strontium cobaltite _{_{_{(Sm x Sr 1-x CoO}}} 3: SSC), lanthanum strontium manganite _{_{_{(La 1-x Sr x MnO}}} 3: LSM It is preferable to apply a perovskite oxide such as However, it is not limited to these, and conventionally known air electrode materials can be applied. In addition, these can be applied individually by 1 type or in combination of multiple types. Furthermore, examples of the electrolyte material include, but are not limited to, cerium oxide (CeO ₂ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), and lanthanum oxide (La ₂ O ₃ ). It is not a thing, but the mixture with oxides, such as various stabilized zirconia and a ceria solid solution, can be used suitably.

As the fuel electrode 12, one that is strong in a reducing atmosphere, permeates the fuel gas, has high electrical conductivity, and has a catalytic action for converting hydrogen molecules into protons can be suitably used. As a constituent material of the fuel electrode, for example, metals such as nickel (Ni), cobalt (Co) and platinum (Pt) may be applied alone, but oxygen represented by yttria stabilized zirconia (YSZ) may be used. It is preferable to apply a cermet mixed with an ionic conductor. By using such a material, the reaction area increases and the electrode performance can be improved. A ceria solid solution such as samaria doped ceria (SDC) or gadria doped ceria (GDC) can be applied instead of yttria stabilized zirconia (YSZ).

As the solid electrolyte layer 13, a layer having gas impermeability and a capability of passing oxygen ions without passing electrons can be suitably used. As a constituent material of the solid electrolyte layer, for example, yttria (Y ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), samaria (Sm ₂ O ₃ ), gadria (Gd ₂ O ₃ ), scandia (Sc ₂ O _3). ) Or the like can be applied as stabilized zirconia. In addition, ceria solid solutions such as samaria doped ceria (SDC), yttria doped ceria (YDC), gadria doped ceria (GDC), bismuth oxide (Bi ₂ O ₃ ), lanthanum gallate (LaGaO ₃ ), lanthanum strontium magnesium gallate _{_{_{_{(La 1-x Sr x Ga}}}} 1-y Mg y O 3: LSMG) or the like may be applied.

In such a solid oxide fuel cell 1, an oxidant gas such as oxygen or air is introduced into the oxidant gas passage 14a, and hydrogen, hydrocarbons, or various liquid fuels are reformed into the fuel gas passage 15a. Fuel gas such as reformed gas obtained is introduced. In the air electrode 11, oxygen gas molecules are decomposed into oxygen ions and electrons at the three-phase interface serving as an active point, and the oxygen ions are transmitted through the solid electrolyte layer 13 and conducted to the fuel electrode 12. Further, in the fuel electrode 12, oxygen ions conducted from the solid electrolyte layer 13 react with fuel gas molecules and electrons at the three-phase interface that is also the active point. Electrical energy can be obtained by electrically connecting the air electrode 11 and the fuel electrode 12 through the air electrode current collector 14 and the fuel electrode current collector 15.

The solid oxide fuel cell 1 of this embodiment includes a fuel electrode 12 and an air electrode 11, a solid electrolyte layer 13 sandwiched between the fuel electrode 12 and the air electrode 11, and a current collector disposed on the air electrode 11 side. (Air electrode current collector 14). Further, the solid oxide fuel cell 1 includes a current collector member 20 that exists between the air electrode 11 and the current collector and has a convex portion 23 formed on the surface on the air electrode side. And between the air electrode 11 and the convex part 23 of the current collection material part 20, the metal thin layer 24 in which the yield stress was smaller than the current collection material part 20, and the plastic region deformed plastically was formed is provided. . In this way, by providing a metal with a small yield stress as a thin metal layer at the interface between the current collector member 20 and the electrode (air electrode) made of a structure in which the convex portion 23 is formed on the surface on the air electrode side, A thin metal layer undergoes plastic deformation. A plastic region formed by plastic deformation of the thin metal layer 24 is formed between the air electrode 11 and the current collector member 20. Therefore, compared with the case where a thin metal layer is not provided, the current collection resistance reduction effect can be enhanced even with the same pressing load. As a result, it is not necessary to use a large-diameter bolt for increasing the pressing load, and the current collection resistance between the electrode and the current collector is reduced while suppressing an increase in the weight and volume of the fuel cell stack. It becomes possible.

In addition, since the current collector member 20 can use an oxidation-resistant metal, even when it is used on the air electrode 11 side, it is possible to suppress oxidation at a high temperature and prevent a decrease in current collecting resistance.

[Method for producing solid oxide fuel cell]
Next, a method for manufacturing the solid oxide fuel cell 1 according to this embodiment will be described. In the present embodiment, the thin metal layer 24 is first formed on the surface of the current collector member 20. Although the formation method of the metal thin layer 24 is not specifically limited, For example, physical vapor deposition method (PVD method), powder jet deposition method (PJD method), thermal spraying method, plating method, electroless plating method, chemical vapor deposition method (CVD method) Etc. can be used.

The thin metal layer 24 may be formed on the entire surface of the current collector 20. However, the metal thin layer 24 should just be provided at least between the current collector part 20 and the air electrode 11. For this reason, masking or the like may be performed on portions other than between the current collector member 20 and the air electrode 11 so that the thin metal layer 24 is not formed. Thereby, the material of the metal thin layer 24 can be reduced.

Next, the air electrode current collector 14, the current collector member 20 provided with the metal thin layer 24, and the air electrode 11 are laminated in this order, and a pressing load is applied to the metal thin layer 24. Thereby, the metal thin layer 24 is plastically deformed, and the contact surface 22 in the plastic region is obtained. At this time, the air electrode current collector 14, the current collector member 20 provided with the thin metal layer 24, the air electrode 11, the solid electrolyte layer 13, and the fuel electrode 12 are laminated in this order, and a pressing load is collectively applied. May be. In this way, the solid oxide fuel cell 1 can be obtained.

As another manufacturing method of the solid oxide fuel cell 1, first, a thin metal layer 24 is formed on the surface of the air electrode 11. Although the formation method of the metal thin layer 24 is not specifically limited, The above-mentioned method can be used. At this time, similarly to the above, masking or the like may be performed except for between the current collector member 20 and the air electrode 11 so that the thin metal layer 24 is not formed. Then, the air electrode current collector 14, the current collector member 20, and the air electrode 11 provided with the metal thin layer 24 are laminated in this order, and a pressing load is applied to the metal thin layer 24, whereby A solid oxide fuel cell can be obtained.

In the present embodiment, the thin metal layer 24 may be formed after the air electrode current collector 14 and the current collector 20 are welded. By welding the air electrode current collector 14 and the current collector member 20 to provide a welded portion 27, the electrical resistance between the air electrode current collector 14 and the current collector member 20 is reduced, and the output of the fuel cell is reduced. It becomes possible to raise more.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Example 1]
First, a current collector was obtained by molding a ferrite plate material (ferritic stainless steel SUS430) having a thickness of 0.01 mm by a pressing method. Further, a mesh (# 100) made of a ferrite material (ferritic stainless steel SUS430) was prepared as a current collector part, and the current collector and the current collector part were previously integrated by welding.

In addition, an air electrode (lanthanum strontium cobalt ferrite: LSCF), a solid electrolyte layer (yttria stabilized zirconia: YSZ), a fuel electrode (cermet of Ni and YSZ particles: Ni—YSZ) and a metal support are laminated in this order. A power generation cell was also prepared. The metal support is a support made of a porous metal in contact with the surface of the fuel electrode opposite to the solid electrolyte layer.

Next, the surface of the current collector 20 other than the surface in contact with the air electrode 11 was coated with a resin layer. Specifically, first, as shown in FIG. 10A, the surface where the current collector 20 contacts the air electrode 11 was coated using a Kapton (registered trademark) tape 31. Next, as shown in FIG. 10B, a resin solution in which a polypropylene resin was dissolved in an organic solvent was prepared and sprayed on the Kapton tape 31 by spraying. Then, the resin layer 32 was formed by performing the drying process for 24 hours or more at normal temperature. And as shown in FIG.10 (c), the resin layer 32 was formed by peeling the Kapton tape 31. FIG.

Then, a thin metal layer was formed on the obtained resin layer 32. Specifically, the power generation cell on which the resin layer 32 was formed was installed in a magnetron sputtering apparatus, and an Ag target was installed in the apparatus. Then, the temperature in the apparatus was controlled from room temperature to a predetermined temperature at an output of 1200 W, and film formation was performed for 60 minutes. As a result, as shown in FIG. 10D, a thin metal layer 24 (silver thin film) having a thickness of about 1 to 2 μm was formed on the air electrode 11 and the resin layer 32.

Next, as shown in FIG. 10 (e), the stack was assembled by pressing the projection 23 of the current collector 20 against the thin metal layer 24 on the air electrode 11. At that time, a specified surface pressure (about 0.3 MPa) was applied so that the convex portion 23 of the current collector member 20 was plastically deformed. After assembling the stack, the fuel electrode 12 side was sealed with an inert gas, and only the air electrode 11 side was fired at 800 ° C. in the atmosphere. As a result, the resin layer 32 disappeared, and the thin metal layer where the current collector 20 and the air electrode 11 were not in contact with each other was peeled off.

Then, by supplying a purge gas (air) with a constant flow rate to the flow path on the air electrode side, an excessive thin metal layer was ejected out of the stack and recovered. Thus, the fuel cell of this embodiment as shown in FIG.

[Example 2]
First, a current collector was obtained by molding a ferrite plate material (ferritic stainless steel SUS430) by a press method in the same manner as in Example 1. Further, a mesh (# 100) made of a ferrite material (ferritic stainless steel SUS430) is prepared as the current collector part, and the air electrode current collector 14 and the current collector part 20 are welded in advance as shown in FIG. And integrated. A power generation cell similar to that in Example 1 was also prepared.

Next, the air electrode current collector 14 and the current collector part 20 are previously integrated by welding, and the other parts than the current collector part 20 are covered with a Kapton sheet and masked, and the thin metal layer 24 is formed on the current collector part 20. Coated. Specifically, the masked current collector 20 was installed in a magnetron sputtering apparatus, and an Ag target was installed in the apparatus. Then, the temperature in the apparatus was controlled from room temperature to a predetermined temperature at an output of 1200 W, and film formation was performed for 60 minutes. As a result, as shown in FIG. 11B, a thin metal layer 24 (silver thin film) having a thickness of about 1 to 2 μm was formed on the current collector 20.

Next, as shown in FIG. 11 (c), the stack was assembled by pressing the convex portion 23 of the current collector 20 onto the air electrode 11. At that time, a specified surface pressure (about 0.3 MPa) was applied so that the convex portion 23 of the current collector member 20 was plastically deformed. Thus, the fuel cell of this embodiment was obtained.

[Example 3]
First, a current collector was obtained by molding a ferrite plate material (ferritic stainless steel SUS430) by a press method in the same manner as in Example 1. Further, a mesh (# 100) made of a ferrite material (ferritic stainless steel SUS430) is prepared as a current collector portion, and the air electrode current collector 14 and the current collector portion 20 are welded in advance as shown in FIG. And integrated. A power generation cell similar to that in Example 1 was also prepared.

Next, masking was performed on portions other than the air electrode side of the current collector part 20 with respect to the one in which the air electrode current collector 14 and the current collector part 20 were previously integrated. Specifically, first, the air electrode current collector 14 and the current collector part 20 were welded and integrated, and portions other than the current collector part 20 were covered with a Kapton sheet. Next, as shown in FIG. 12B, a resin solution in which a polypropylene resin was dissolved in an organic solvent was prepared and sprayed on the current collector 20 by spraying. Then, the resin layer 32 was formed by performing the drying process for 24 hours or more at normal temperature. And as shown in FIG.12 (c), the blasting process using the spray spraying method was implemented with respect to the air electrode 11 side of the resin layer 32, and a part of resin layer 32 was peeled.

Then, a thin metal layer was formed on the current collector part 20 partially masked with the resin layer 32. Specifically, the masked current collector 20 was installed in a magnetron sputtering apparatus, and an Ag target was installed in the apparatus. Then, the temperature in the apparatus was controlled from room temperature to a predetermined temperature at an output of 1200 W, and film formation was performed for 60 minutes. As a result, as shown in FIG. 12D, a metal thin layer 24 (silver thin film) having a film thickness of about 1 to 2 μm was formed on the current collector 20 and the resin layer 32.

The current collector part 20 on which the thin metal layer 24 was formed and the air electrode current collector 14 were integrated and fired at 800 ° C. in the atmosphere. As a result, the resin layer 32 disappeared, and the metal thin layer 24 at the portion masked by the current collector 20 and the resin layer 32 was peeled off. Then, the thin metal layer 24 that has been peeled off is removed by applying an air flow, and the Kapton sheet that covers a portion other than the current collector 20 is further peeled off, thereby forming the thin metal layer 24 as shown in FIG. (Silver thin film) was formed only on the air electrode side of the current collector 20.

Next, as shown in FIG. 12 (f), the stack was assembled by pressing the convex portion 23 of the current collector portion 20 onto the air electrode 11. At that time, a specified surface pressure (about 0.3 MPa) was applied so that the convex portion 23 of the current collector member 20 was plastically deformed. Thus, the fuel cell of this embodiment was obtained.

[Comparative example]
First, a current collector was obtained by molding a ferrite plate material (ferritic stainless steel SUS430) having a thickness of 0.01 mm by a pressing method. Further, a mesh (# 100) made of a ferrite material (ferritic stainless steel SUS430) was prepared as a current collector part, and the current collector and the current collector part were previously integrated by welding. A power generation cell similar to that in Example 1 was also prepared.

Next, the stack was assembled by pressing the convex part of the current collector part onto the air electrode. At that time, a specified surface pressure (about 0.3 MPa) was applied so that the convex portion of the current collector portion was plastically deformed. Thus, the fuel cell of this embodiment was obtained. That is, the fuel cell of the present embodiment is one in which a thin metal layer is not provided with respect to the fuel cell of Example 1.

In the fuel cells of Examples 1 to 3 and the comparative example, the separator contact ratio shown in Formula 1 was adjusted to 20%.
[Equation 1]
[Separator contact ratio] (%) = [Area of contact surface between thin metal layer or current collector part and air electrode] / [Area of surface facing current collector in air electrode] × 100

[Evaluation]
With respect to the fuel cells obtained in Example 1 and the comparative example, as shown in FIG. 13, a metal layer 40 made of a metal plate was laminated on the surface of the air electrode current collector 14 opposite to the current collector part 20. And the current collection resistance (ASR) between the metal layer 40 and the metal support laminated | stacked on the fuel electrode 12 was measured. The current collecting resistance was measured by setting the voltage between the metal layer 40 and the metal support to 4 V and changing the current up to 1 A under a constant voltage load. In addition, the temperature at the time of measuring current collection resistance was 750 degreeC.

As shown in FIG. 14, while the fuel cell of Example 1 is the collector resistance is about 2.07 × ^{10 -2} Ωcm ^2, the fuel cell of Comparative Example collector resistance 2.27 × 10 ^- It was about ² Ωcm ² . Thus, it can be seen that by providing a metal thin layer (silver thin film) having a yield stress smaller than that of the current collector part and the air electrode, the current collection resistance is reduced by about 10% and the power generation performance can be improved.

As described above, the contents of the present invention have been described along a plurality of embodiments. However, the present invention is not limited to these descriptions, and it is obvious to those skilled in the art that various modifications and improvements can be made. is there.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 10 Single cell 11 Air electrode 12 Fuel electrode 13 Solid electrolyte layer 14 Air electrode current collector 20 Current collector part 23 Convex part 24 Metal thin layer

Claims

A fuel electrode and an air electrode;
A solid electrolyte layer sandwiched between the fuel electrode and the air electrode;
A current collector disposed on the air electrode side;
A current collector part that exists between the air electrode and the current collector and has a convex part formed on the surface on the air electrode side;
With
Between the air electrode and the convex part of the current collector part, a thin metal layer in which a yield stress is smaller than that of the current collector part and a plastic region deformed plastically is formed is provided. Solid oxide fuel cell.
2. The solid oxide fuel cell according to claim 1, wherein the current collector part is made of an alloy containing at least one of chromium and iron as a main component.
3. The solid oxide fuel cell according to claim 1, wherein the thin metal layer has a thickness of 0.01 μm or more.
The thin metal layer is composed of at least one selected from the group consisting of silver, platinum and gold, or an alloy containing at least one of silver, platinum and gold and at least one of palladium, ruthenium and cobalt. The solid oxide fuel cell according to any one of claims 1 to 3.
The current collector part has a cross-sectional shape along the stacking direction of the air electrode, the current collector part and the current collector that is triangular, semicircular or trapezoidal and has a cross section perpendicular to the stacking direction. 5. The solid oxide fuel cell according to claim 1, wherein the area decreases from the current collector toward the air electrode. 6.
A method for producing a solid oxide fuel cell according to any one of claims 1 to 5,
A method for producing a solid oxide fuel cell, comprising forming the metal thin layer after welding the current collector and the current collector portion.