JP2007273423A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of improving diffusion of gas with a simple structure in the solid oxide fuel cell in which a plurality of unit cells are laminated. <P>SOLUTION: The solid oxide fuel cell in which a mixed gas of fuel gas and oxidant gas is supplied includes a plurality of unit cells in which a fuel electrode 12 and an air electrode 13 are formed respectively on both sides of electrolyte 11 of sheet-shape, and an inter-connector 2 which is interposed between the unit cells 1 and connects electrically the plurality of unit cells 1 in series. The inter-connector 2 is porous and a plurality of through holes 14 which penetrate through the fuel electrode 12, the electrolyte 11, and the air electrode 13 from one face and are open to the other face are formed in the unit cells 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell that generates power using a mixed gas of a fuel gas and an oxidant gas.

  In recent years, a single-chamber SOFC has been proposed in which a gas supply line can be simplified and a simple system structure can be realized by mixing and supplying fuel gas and oxidant gas without requiring a separator or a gas seal material. Yes. The fuel cell employed in this single-chamber SOFC has two electrodes, a fuel electrode and an air electrode, which are exposed to a mixed gas of fuel gas and oxidant gas, and have gas selectivity between them. Is characterized by the generation of voltage.

For example, Patent Document 1 describes the following single-chamber fuel cell. In this battery, a plurality of unit cells each having a fuel electrode and an air electrode formed on both sides of the plate electrolyte are connected in series and accommodated in a container. The fuel electrode and the air electrode are formed with a flow path through which gas passes, and the electrolyte is penetrated to flow the gas that has passed through the flow path of one electrode to the flow path of the other electrode. A hole is formed in the peripheral edge. And the mixed gas supplied from the supply port formed in the one end part of the container passes through the plurality of single cells and is discharged from the discharge port formed in the other end part of the container. In the process, the mixed gas enters the electrode from the flow path of one electrode and flows into the flow path of the other electrode through the through hole of the electrolyte, thereby generating power in contact with both electrodes.
Japanese Patent No. 3530834

  However, in the battery, since the through-hole is formed only in the peripheral edge portion of the electrolyte, there is a problem that the amount of gas flowing from one electrode to the other electrode is limited, and the gas fluidity is reduced. Therefore, there is a problem that gas diffusibility is small and the output obtained is not large.

  The present invention has been made to solve the above problems, and in a solid oxide fuel cell having a structure in which a plurality of single cells are stacked, a solid that can improve gas diffusibility with a simple configuration. An object is to provide an oxide fuel cell.

  The present invention is a solid oxide fuel cell to which a mixed gas of a fuel gas and an oxidant gas is supplied, and has been made in order to solve the above problem. A plurality of single cells in which an electrode (anode) and an air electrode (cathode) are formed, and an interconnector interposed between the single cells to electrically connect the plurality of single cells in series. The interconnector is porous, and each unit cell is formed with a plurality of through-holes that penetrate the fuel electrode, electrolyte, and air electrode from one side and open to the other side.

  According to this configuration, since a plurality of through holes penetrating each single cell are formed, gas can be smoothly circulated from one surface of the single cell to the other surface. In addition, since the interconnector disposed between the single cells is porous, the gas is easily diffused, and the gas can be sufficiently supplied to the electrodes of the single cells in contact therewith. Therefore, when a plurality of single cells are stacked, gas can be sufficiently supplied to each single cell, and a high output can be obtained.

  In the battery, it is preferable that the fuel electrode and the air electrode have porosity. By doing so, gas can be sufficiently diffused in each electrode, and all regions of the electrode related to power generation can be used effectively in power generation. At this time, the porosity of the fuel electrode and the air electrode is preferably 30 to 70%. Moreover, it is preferable that thickness is 0.2-3 mm from a viewpoint of fully diffusing gas.

  Moreover, it is preferable to arrange | position the current collection layer which has porous property in the both ends of the lamination direction of a some single cell, respectively. With this configuration, for example, when a mixed gas is supplied in the stacking direction of a single cell, the supplied mixed gas enters the porous current collecting layer, so that the gas easily diffuses. Gas can be sufficiently supplied to the entire surface.

  In addition, the apparatus may further include a casing that accommodates a plurality of single cells and interconnectors, and that has gas supply ports and discharge ports formed at both ends in the stacking direction of the plurality of single cells. As described above, in the fuel cell according to the present invention, the through holes are formed in parallel to the stacking direction of the single cells. Therefore, when the single cell is accommodated in the casing having the above configuration, the gas supply direction and the through holes are parallel. Thus, the gas can be smoothly distributed. Further, since the gas is supplied into the casing, the gas can be intensively supplied to each single cell, and efficient use of the gas becomes possible. As a result, a high output can be obtained.

  The interconnector is a porous substrate, and is preferably a conductive ceramic or metal. The interconnector is porous, but the porosity is preferably 10 to 80%. This is because if the porosity is less than 10%, the gas permeability is deteriorated and the electrode reaction is lowered. On the other hand, if the porosity is more than 80%, the number of electron transfer paths is reduced. This is because the resistance increases and the conductivity decreases. Furthermore, the thickness of the interconnector is preferably 0.1 to 3 mm from the viewpoint of gas diffusion. If it is smaller than 0.1 mm, the gas diffusibility is deteriorated. If it is larger than 3 mm, the resistance in the thickness direction is increased, so that the conductivity is lowered and the stack performance is lowered.

  According to the present invention, in a solid oxide fuel cell having a structure in which a plurality of single cells are stacked, gas diffusivity can be improved with a simple configuration.

  Hereinafter, an embodiment of a solid oxide fuel cell and a fuel cell unit according to the present invention will be described with reference to the drawings. 1 is a cross-sectional view of a solid oxide fuel cell according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1, the solid oxide fuel cell according to this embodiment includes a plurality of single cells 1 (two in the figure) and an interconnector 2 that electrically connects them in series. Yes. In addition, current collecting layers 3 are disposed at both ends of the unit cell 1 in the stacking direction (vertical direction in FIG. 1). The single cell 1, the interconnector 2, and the current collecting layer 3 are accommodated in the casing 4. Each single cell 1 is configured by forming a thin film fuel electrode 12 and an air electrode 13 on both surfaces of a rectangular sheet-like electrolyte 11. As shown in FIG. 2, each unit cell 1 is formed with a plurality of through holes 14 having openings in the fuel electrode 12 and the air electrode 13.

  The interconnector 2 is formed in a rectangular sheet shape having substantially the same area as each single cell, and is inserted between the single cells 1. The interconnector 2 is formed of a conductive porous body. The current collecting layer 3 is also made of the same size and material as the interconnector 2.

  The casing 4 accommodates the single cell 1, the interconnector 2, and the current collecting layer 3 in a laminated structure as described above with almost no gap, and gas supply ports 41 and discharge ports 42 are provided at both ends in the stacking direction. Each is formed. That is, the current collecting layers 3 disposed at both ends of the plurality of single cells 1 face the outside through the supply port 41 and the discharge port 42. Therefore, the mixed gas flowing from the supply port 41 is first supplied to the current collecting layer 3. In addition, a conductive wire 5 is connected to both current collecting layers 3 via a supply port 41 and a discharge port 42.

  Next, materials constituting the fuel cell will be described. As the material of the electrolyte 11, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria-based oxides doped with samarium or gadolinium, lanthanum galade-based doped with strontium or magnesium Oxygen ion conductive ceramic materials such as oxides, zirconia-based oxides containing scandium and yttrium can be used.

  The fuel electrode 12 and the air electrode 13 can be formed of a ceramic powder material. The average particle size of the powder used at this time is preferably 10 nm to 100 μm, more preferably 50 nm to 50 μm, and particularly preferably 100 nm to 10 μm. In addition, an average particle diameter can be measured according to JISZ8901, for example.

  As the fuel electrode 12, for example, a mixture of a metal catalyst and a ceramic powder material made of an oxide ion conductor can be used. As the metal catalyst used at this time, a material that is stable in a reducing atmosphere, such as nickel, iron, cobalt, or a noble metal (platinum, ruthenium, palladium, etc.) and has hydrogen oxidation activity can be used. In addition, as the oxide ion conductor, one having a fluorite structure or a perovskite structure can be preferably used. Examples of those having a fluorite structure include ceria-based oxides doped with samarium, gadolinium, and the like, and zirconia-based oxides containing scandium and yttrium. In addition, examples of those having a perovskite structure include lanthanum galide oxides doped with strontium and magnesium. Among the materials described above, the fuel electrode 12 is preferably formed of a mixture of an oxide ion conductor and nickel. The mixed form of the ceramic material made of the oxide ion conductor and nickel may be a physical mixed form, or may be a powder modification to nickel or a nickel modification to ceramic material. Good. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. Further, the fuel electrode 12 can also be configured using a metal catalyst alone.

As the ceramic powder material forming the air electrode 13, for example, a metal oxide made of Co, Fe, Ni, Cr, Mn or the like having a perovskite structure or the like can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) (Fe, Co) O ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  The fuel electrode 12 and the air electrode 13 are formed by adding appropriate amounts of a binder resin, an organic solvent, and the like with the above-described material as a main component. More specifically, it is preferable to add a binder resin or the like so that the main component is 50 to 95% by weight in the mixing of the main component and the binder resin.

  As a method for forming the fuel electrode 12 and the air electrode 13, for example, a printing method can be used. Specifically, a printing method such as a screen printing method, a knife coating method, a doctor blade method, or a spray coating method can be used. it can. In addition, the electrode can be formed by applying the fuel electrode 12 and the air electrode 13 on a transfer sheet (so-called green body) and transferring them.

The interconnector 2 and the current collecting layer 3 have electronic conductivity, but it is preferable that the ion conductivity is small enough to be ignored. Moreover, it is preferable to be comprised with the thermodynamically stable material. The conductivity is preferably 2 S · cm ⁻¹ or more at the operating temperature of the fuel cell. While satisfying such requirements, each layer can be configured as follows. In addition, the porosity of the interconnector is preferably in the range of 10 to 80%, more preferably in the range of 30 to 70%, considering the gas permeability and the strength of the interconnector. From the viewpoint of gas diffusion, the thickness is preferably 0.1 to 3 mm, and more preferably 0.2 to 1 mm. In order to satisfy such a requirement, the material constituting the interconnector 2 is a conductive metal such as Pt, Au, Ag, Ni, Cu, SUS, or a metal-based material, or La (Cr, Mg) O ₃ , ( It can be formed of a lanthanum chromite-based conductive ceramic material such as La, Ca) CrO ₃ , (La, Sr) CrO _3, and one of these may be used alone. You may mix and use a seed | species or more.

  The casing 4 is made of an insulating material. For example, a general heat-resistant glass such as quartz glass or Vycor glass, or a ceramic plate such as alumina, silicon nitride, or silicon carbide can be used.

  The fuel cell configured as described above generates power as follows. First, a mixed gas G of a fuel gas composed of hydrogen or a hydrocarbon such as methane or ethane and an oxidant gas such as air is supplied to the supply port 41 of the casing 4 at a high temperature (for example, 400 to 1000 ° C.). To do. The mixed gas G contacts the fuel electrode 12 of the upper unit cell 1 while diffusing in the current collecting layer 3. Here, the mixed gas G flows out to the air electrode 13 side through the through hole 14 while diffusing in the porous fuel electrode 12. Since the air electrode 13 is also porous, the mixed gas G flows into the interconnector 2 while diffusing in the electrode 13. Also in the interconnector 2, the mixed gas G enters the fuel electrode 12 of the lower unit cell 1 while diffusing in the plane direction, and flows out to the air electrode 13 side through the through hole 14. Thus, it flows out of the casing 4 through the discharge port 42. In this process, since the fuel electrode 12 and the air electrode 13 are in contact with the mixed gas G, oxygen ion conduction through the electrolyte 11 occurs between the fuel electrode 12 and the air electrode 13 in each unit cell 1 to generate power. Is done.

  As described above, according to this embodiment, since the plurality of through holes 14 penetrating each single cell 1 are formed, the surface of the single cell 1 on the fuel electrode 12 side to the surface on the air electrode 13 side. Gas can be distributed smoothly. Further, since the interconnector 2 disposed between the single cells 1 is porous, the gas is easily diffused, and the mixed gas G can be sufficiently supplied to the electrodes of the single cells 1 that are in contact with the interconnector 2. Become. Therefore, when a plurality of single cells 1 are stacked, the mixed gas G can be sufficiently supplied to each single cell 1 and a high output can be obtained.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, A various change is possible unless it deviates from the meaning. For example, in the above-described embodiment, the porous current collecting layer 3 is disposed at both ends of the single cell 1. Since it is good, for example, one formed in a mesh shape can also be used. Alternatively, if a gap is formed between the wall surface on the supply port 41 side and the upper unit cell 1 without providing a current collecting layer, the gas diffuses in this gap and the gas is brought into contact with the entire surface of the fuel electrode 12. be able to. However, in order to increase the current collection efficiency, it is preferable to provide a current collection layer.

1 is a cross-sectional view showing an embodiment of a solid oxide fuel cell according to the present invention. It is the sectional view on the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single cell 11 Electrolyte 12 Fuel electrode 13 Air electrode 14 Through-hole 2 Interconnector 3 Current collecting layer 4 Casing 41 Supply port 42 Discharge port

Claims (7)

A solid oxide fuel cell to which a mixed gas of a fuel gas and an oxidant gas is supplied,
A plurality of unit cells in which a fuel electrode and an air electrode are formed on both surfaces of a sheet-like electrolyte, and
An interconnector interposed between the single cells and electrically connecting the plurality of single cells in series,
The interconnector is porous, and
A solid oxide fuel cell, wherein the single cell is formed with a plurality of through-holes penetrating the fuel electrode, electrolyte, and air electrode from one side thereof and opening on the other side.   The solid oxide fuel cell according to claim 1, wherein the fuel electrode and the air electrode are porous.   3. The solid oxide fuel cell according to claim 1, wherein a current collecting layer having a porous property is disposed at both ends in the stacking direction of the plurality of single cells. 4.   4. The apparatus according to claim 1, further comprising a casing that accommodates the plurality of single cells and the interconnector and has gas supply ports and discharge ports formed at both ends in the stacking direction of the plurality of single cells. The solid oxide fuel cell as described.   The solid oxide fuel cell according to any one of claims 1 to 4, wherein the interconnector is a porous substrate and is made of conductive ceramics or metal.   The solid oxide fuel cell according to any one of claims 1 to 5, wherein the interconnector has a porosity of 10 to 80%.   The solid oxide fuel cell according to any one of claims 1 to 6, wherein a thickness of the interconnector is 0.1 to 3 mm.

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