Patent Application
20080038621
a) is a front view showing a supporting member 1,
a) is a perspective view showing an electrochemical cell 11,
a) is a cross sectional view showing a supporting member 1 and an electrochemical cell 11,
a) is a plan view showing a manifold member 20, and
According to the present invention, the electrochemical cell has planar shape, which is not limited to a flat plate and includes a curved sheet and arc-shaped sheet. According to the present invention, the electrochemical cell has a first electrode contacting a first gas, a sold electrolyte film and a second electrode contacting a second gas.
The first and second electrodes are selected from an anode and a cathode. In the case that one of these is an anode, the other is a cathode. At the same time, the first and second gases are selected from an oxidizing gas and a reducing gas.
The oxidizing gas is not particularly limited as far as oxygen ions can be supplied to a solid electrolyte film from the gas. The gas includes air, diluted air, oxygen and diluted oxygen. The reducing gas includes hydrogen, carbon monoxide, methane or the mixtures thereof.
An electrochemical cell means a cell performing an electrochemical reaction, in the invention. For example, an electrochemical cell includes an oxygen pump and a high temperature vapor electrolyte cell. The high temperature vapor electrolyte cell can be used as a hydrogen production device, and also as a removing system of water vapor. Further, the electrochemical cell can be used as a decomposition cell for NOX, SOX. This decomposition cell can be used as a purification apparatus for discharge gas from motor vehicles, power generation devices or the like. In this case, oxygen in the discharge gas is removed through a solid electrolyte film while NOX is electrolyzed into N2 and O2−, and the oxygen thus produced by this decomposition can be also removed. Further, by this process, vapor in the discharge gas is electrolyzed to produce hydrogen and oxygen, and the produced hydrogen reduces NOX to N2. Further, in a preferable embodiment, the electrochemical cell is a solid oxide fuel cell.
The material for a solid electrolyte is not limited particularly, and includes any oxide ion conductor. For example, it may be yttria-stabilized zirconia or yttria partially-stabilized zirconia. In the case of NOx decomposition cell, cerium oxide is also preferable.
The cathode material is preferably lanthanum-containing perovskite-type composite oxide, more preferably lanthanum manganite or lanthanum cobaltite, and most preferably lanthanum manganite. Into lanthanum cobaltite and lanthanum manganite, strontium, calcium, chromium, cobalt (in the case of lanthanum manganite), iron, nickel, aluminum or the like may be doped. Further, the cathode material may be palladium, platinum, ruthenium, platinum-zirconia cermet, palladium-zirconia cermet, ruthenium-zirconia cermet, platinum-cerium oxide cermet, palladium-cerium oxide cermet, and ruthenium-cerium oxide cermet.
As the anode materials, platinum-zirconia cermet, platinum, nickel, nickel-zirconia cermet, platinum-cerium oxide cermet, nickel-cerium oxide cermet, ruthenium, ruthenium-zirconia cermet and the like are preferable.
The construction of each electrochemical cell is not particularly limited. The electrochemical cell may be consisting of three layers of an anode, a cathode and a solid electrolyte layer. Alternatively, the electrochemical cell may have, for example, a porous layer in addition to the anode, cathode and solid electrolyte layer.
The construction of the metal supporting member supporting the electrochemical cell is not particularly limited. Further, a metal forming the supporting member is not limited as far as it is resistant against oxidation and reduction at a working temperature of the electrochemical cell. The metal may be pure metal or an alloy, and may preferably be nickel, a nickel based alloy such as Inconel and Nichrome, an iron based alloy such as stainless steel or a cobalt based alloy such as Stellite.
The shape of the metal manifold member supporting the supporting member is not particularly limited. Although the shape may preferably be a flat plate, the planar shape is not particularly limited. The gas supply hole and gas discharge hole both communicated with the flow route for the first gas are provided in the manifold member, and number, dimension and position of the supply and discharge holes are not particularly limited. Further, the metal forming the manifold member is not limited as far as it is resistant against oxidation and reduction at a working temperature of the electrochemical cell. The metal may be pure metal or an alloy, and may preferably be nickel, a nickel based alloy such as Inconel and Nichrome, an iron based alloy such as stainless steel or a cobalt based alloy such as Stellite.
According to a preferred embodiment, a plurality of supporting members are provided on a single manifold member. Further, according to a preferred embodiment, a flow route for the second gas is formed between the supporting members. The gas seal structure can be thereby further simplified.
According to a preferred embodiment, an interconnector is provided between a plurality of supporting members, and the flow route for the second gas is formed between the interconnector and electrochemical cell. Further, according to a preferred embodiment, the interconnector and the adjoining supporting member are electrically connected with each other by the electric collecting member so that a plurality of electrochemical cells can be easily connected in series.
According to a preferred embodiment, it is provided a seal member for sealing the interconnector and the supporting member in air-tight manner. Although the material of the seal member is not particularly limited, it is required resistance against oxidation and reduction at the operating temperature of the electrochemical cell. Specifically, it may be listed a glass containing silica as main component, crystallized glass, metal solder or the like. It may be further listed an O-ring, a C-ring, an E-ring, or a compression sealing member such as a metal jacket gasket, a mica gasket or the like.
a) is a front view showing a supporting member 1,
Gas supplied from a manifold member described later is supplied through the supply hole 2 as an arrow A, flown in the groove 4 as an arrow B, and then flown from the groove 4 to the groove 5 as an arrow C. The gas is then flown in the groove 5 as an arrow D and discharged through the discharge hole 3 as an arrow E into the manifold member.
a) is a perspective view showing an electrochemical cell 11 used in the present example. The electrochemical cell 11 has a first electrode 12, a solid electrolyte layer 13 and a second electrode 14. The electrochemical cell 11 may have an additional part such as a porous substrate.
b) is a perspective view showing a sealing member 8 used in the present example. A space 8a is formed in the seal member 8 for containing and surrounding the cell 11 in the space 8a.
That is, as shown in
According to the present example, the permeable and conductive material 10 is contained in the flow route 6 so that the supporting member 1 is conducted to the first electrode 12 of the cell 11 (not shown in
The conductive and permeable material includes a metal such as nickel, a nickel-based alloy such as Inconel, Nichrome or the like, or an iron-based alloy such as stainless steel, and a conductive ceramics such as lanthanum chromite. Further, the shape of the permeable material includes felt, porous sintered body, mesh or the like.
Then, as shown in
a) is a plan view showing a manifold member 20, and
A supply hole 25 and a discharge hole 26 for the second gas are formed at the side face of the manifold member 20. A supply tube portion 27 is extended from the supply hole, and a predetermined number of gas supply holes 23 are extended upwardly from the supply tube portion 27. Further, a discharge tube portion 28 is extended from the discharge hole 26, and a predetermined number of discharge holes 24 are formed upwardly from the discharge tube portion 28.
A predetermined number of the assemblies 30 shown in
For example, it is provided that SOFC is used as the cell, oxidizing gas is flown in the spaces between the supporting members and fuel gas is flown into the flow routes between the supporting members and electrochemical cells, respectively. In this case, electrons (carried as oxygen ions in solid electrolyte layer) are flown through the cathode 12 and the solid electrolyte layer 13 as shown in
According to the embodiments described above, the ceramic electrochemical cell 11 is supported with the metal supporting member 1, and the gas flow route 6 is formed between the supporting member 1 and the electrochemical cell 11. The gas supply hole 23 and the gas discharge hole 24 are formed in the metal manifold member 20 so that the holes are communicated with the gas flow route 6. It is thus possible to perform the gas supply into and the gas discharge from the manifold member 20. Further, each electrochemical cell 11 is supported with the metal supporting member 1 and the supporting member 1 is fitted to the manifold member 20. It is thus possible to stack many supporting members and electrochemical cells.
It is thereby possible to avoid excessive load onto each electrochemical cell 11 and the fracture of the cells, so that many cells can be stacked together. Moreover, the flow route 6a for the first gas is formed between the adjacent cell 11 and supporting member 1, and the metal manifold 20 and supporting members 1 are connected with each other to provide manifold structure for performing the supply of the gas into and the discharge of the gas from the flow route. The gas seal structure can be thereby simplified.
(Production of Anode Substrate)
50 weight parts of nickel oxide powder having an average particle size of 1 μm and 50 weight parts of yttria-stabilized zirconia (8YSZ, “TZ-8Y: Tosoh) were mixed, and polyvinyl alcohol (PVA) as a binder and pure water were added thereto to obtain slurry. The slurry was dried and granulated with a spray drier to obtain powder for anode substrate. The powder was subjected to press molding to obtain a flat plate having a length of 150 mm, a width of 150 mm and a thickness of 1.5 mm. Thereafter, the flat plate was sintered at 1400° C. in air for 3 hours to obtain an anode substrate 12.
8 mol % yttria stabilized zirconia (8YSZ) powder was used as a material for solid electrolyte. Water and a binder were added to the 8YSZ powder and then mixed for 16 hours in a ball mill. The thus obtained slurry was applied and dried on the anode substrate 12 and then subjected to sintering at 1400° C. in air for 2 hours to obtain a solid electrolyte layer 13 having a thickness of 10 μm. The thus obtained substrate was subjected to grinding to obtain a sintered body of the anode substrate 12 and solid electrolyte film 13. The sintered body has a length of 100 mm, a width of 100 mm and a thickness of 1 mm.
Ethyl cellulose as a binder and terpineol as a solvent were added to cathode material of La0.8Ca0.2MnO3 (LCM) powder having an average particle diameter of 1 μm to obtain paste. The paste was shaped to a film by screen printing to a size of 90 mm and 90 mm. The film was dried and sintered at 1200° C. for 1 hour to obtain a planar cell 11 having the anode substrate 12, the solid electrolyte 13 and an cathode 14.
It was produced the supporting member 1 shown in
An SUS 430 plate having a length of 130 mm, a width of 130 mm and a length of 3 mm was processed as shown in
The assembly 30 was produced as described above referring to
An SUS 430 plate having a width of 150 mm, a length of 300 mm and a thickness of 15 mm was processed as shown in
Twenty assemblies 30 described above were mounted on the metal manifold member 20 to produce a stack. The bottom face of the supporting member 1 was mounted on the manifold member 20. The fuel supply hole 2 of the supporting member 1 was thus communicated with the fuel supply hole 23 of the manifold member 20, and the fuel supply hole 3 of the supporting member 1 was communicated with the fuel discharge hole 24 of the manifold member. An insulating glass sealing member was inserted between the metal manifold member 20 and the supporting member 1 upon the fixing of each assembly for the sealing and electrical insulation of the metal manifold member 20 and the supporting member 1. Stainless steel plates were used as the electrical collecting members 35.
The sintered body of the solid electrolyte 13/anode substrate 12 produced as described above was processed to a piece of a length of 100 mm, a width of 100 mm and a thickness of 1 mm. The cathode having a length of 90 mm and a width of 90 mm was formed as described in the section of “production of cathode” to produce a planar cell.
A plate made of SUS430 having a length of 120 mm, a width of 120 mm and a thickness of 6 mm was processed. That is, four gas flow routes each having a width of 10 mm and a length of 90 mm were formed in the peripheral portion, and eight grooves for gas flow each having a width of 5 mm and a depth of 2 mm were formed from the gas flow routes, respectively, to produce an interconnector. Air is flown over the surface side and fuel is flown over the back side of the interconnector. The planar cell was mounted in the center of the metal interconnector. Twenty planar cells and twenty interconnectors were alternately laminated and then fixed using stack-fixing bolts to provide an integrated body. Insulating glass seal was used for the gas sealing of the stack.
Fuel gas was supplied to the anode side of the cell through a supply tube for fuel gas provided in the interconnector, and then discharged through a fuel gas discharge tube to the outside of the stack. Air was supplied to the cathode side of the cell through an air supply tube provided in the interconnector, and then discharged through an air discharge tube to the outside of the stack.
The stack was set in an electrical furnace. A voltage cable and a current cable were connected to each of the supporting member and interconnectors provided in both sides of the stack. N2 was flown in the anode side and air was flown in the cathode side while the temperature was elevated to 800° C. At the time point that the temperature reached 800° C., H2 was flown in the anode side to perform the reduction treatment. After three hours of reduction treatment, it was evaluated the current-voltage property of the stack. Further, the stack was subjected to 10 thermal cycles each including one temperature ascending step and one descending step. After the 10 thermal cycles, the current-voltage property of the stack was evaluated and the fracture of the cell was confirmed. Table 1 shows the generation property at 800° C. and the observation of fracture of the cell after the temperature descending step. Further, table 2 shows the change of OCV of each of the stacks (20 cells) according to the inventive and comparative examples.
According to the inventive examples, it was obtained a higher generation power compared with that of the comparative example. Further, according to the comparative example, it was observed a considerable reduction of OCV in three of the stacks. It was thus considered that the cell was broken. It was considered that an excessive stress was applied, at some points, exceeding the fracture stress on the cell to induce the fracture during the assembling of the cells and interconnectors.
Further, after the stacks were subjected to the ten thermal cycles, a reduction of generation power was hardly observed according to the inventive example and a further reduction of the output was observed according to the comparative example. A reduction of OCV of the stack was not observed according to the inventive example. A considerable reduction of OCV was observed in six out of twenty samples according to the comparative example. The presence of the fracture of the cells was observed after the thermal cycle test. As a result, the fracture was not observed in all of the twenty cells according to the inventive example, and the fracture was observed in six out of the twenty cells according to the comparative example.
As described above, according to the present invention, it is possible to prevent the unbalance and local concentration of the stress caused by lamination of the whole cells and to provide a stack of excellent reliability by preventing the fracture of cells.
The present invention has been explained referring to the preferred embodiments, however, the present invention is not limited to the illustrated embodiments which are given by way of examples only, and may be carried out in various modes without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-218344 | Aug 2006 | JP | national |
