Reversible solid oxide fuel cell stack and method for preparing same

a solid oxide fuel cell and stack technology, applied in the direction of fuel cells, cells, electrical equipment, etc., can solve the problems of deterioration of electrical performance, high fabrication cost, and high cost of said processes, and achieve improved mechanical stability, cost-effective effect, and high electrical performan

Inactive Publication Date: 2013-01-31
DANMARKS TEKNISKE UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0144]1. The manufacturing process is simplified; a sealed monolithic stack is manufactured using only one sintering step;
[0145]2. The obtained stack has little or no glass sealing and consists predominantly of metal, making it very mechanically robust;
[0146]3. The stack can be delivered ‘ready-to-use’ as a single component;
[0147]4. Interface reactions between electrodes and electrolyte or interconnect and electrodes are prevented or limited by the impregnation after sintering of the porous structure / stack. This results in the formation of high surface area and thus high performing electrodes.
[0148]5. The process is very flexible;
[0149]6. The high metal content lowers the overall price of the stack;
[0150]7. The high metal content ensures that the current path through a stack is predominantly through metal, which has a high conductivity. This can make non-planar designs attractive, i.e. variants of tubular cells, even though the current paths are longer.
[0151]8. The obtained reversible solid oxide fuel cell monolithic stack is suitable to be used under pressurised conditions, such as in a gas turbine plant. Thereby, a combined cycle plant achieves very high electrical efficiencies and the plant can in addition be simplified.
[0152]In the following, the present invention will be further illustrated with reference to detailed examples. The invention is however not restricted thereto.

Problems solved by technology

Several properties are required for the SOFC's, such as high conductivity, a large area of electrochemically active sites at the electrode / electrolyte interface, chemical and physical stability over a wide range of fuel atmospheres, and minimal microstructural changes with operating time, since such changes are often accompanied by deterioration of electrical performance.
However, said processes are very expensive, and thus there has been a desire to lower the fabrication costs.
1. True monolithic planar stacks are not obtained since the mechanical integrity of the stacks requires a permanent mechanical load to maintain sealing and electrical contact during operation.
2. The manufacturing processes are complicated and comprise numerous sintering steps or expensive chemical or physical deposition techniques.
3. In the case of sintering of the electrodes, there are two drawbacks:a. Due to the required sintering temperatures, performance limiting interface reactions are often observed between the electrodes and the electrolyte and / or interconnect;b. During sintering it is not possible to maintain sufficient fine microstructures in the electrode and in the electrode / electrolyte interface due to excessive grain growth.

Method used

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  • Reversible solid oxide fuel cell stack and method for preparing same
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  • Reversible solid oxide fuel cell stack and method for preparing same

Examples

Experimental program
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first embodiment

[0088]The first embodiment of the present invention is directed to a method for preparing a flat plate design SOFC stack with an external manifolding, and to a SOFC monolithic stack obtainable therewith.

[0089]The stack is made up of two components. The first component comprises at least one porous metal-containing layer 1. Preferably, the first component comprises at least two porous metal-containing layers 1 and 2, and more preferred the component comprises at least three porous metal-containing layers 1, 2 and 3. The component has a graded, porous structure. The grading is made by combining a number of layers which can be varied with respect to the composition, such as metal; electrolyte-metal; porosity, such as filler elements, the addition of tubes / fibers which burn away during sintering; and layer thickness. The thicknesses of layer 1 and 2 are in the range of about 20-70 μm and more preferably about 30-40 μm. The thickness of layer 3 is in the range of about 200-1000 μm, prefe...

second embodiment

[0115]The second embodiment of the present invention is directed to a method for preparing a flat plate design SOFC stack with an internal manifolding, and to a SOFC stack obtainable therewith.

[0116]In this case, the at least one porous metal containing layer 1 of the first component of the second embodiment corresponds to the one as described above for the first embodiment. In a first step, gas distribution holes are punched into opposite sides, as shown in FIG. 5. The diameter of the holes is typically about 5-7 mm, but may vary in the range of 1-10 mm. Next, the electrolyte layer 4 is deposited on top of the metal containing layer with the gas distribution holes in it. Thereby, the punched gas distribution holes and the four sides of the component are also sealed, as shown in FIG. 6.

[0117]Thereafter, a sealing layer 6 is deposited on the electrolyte layer 4, as shown in FIG. 7. The sealing layer 6 is a thin layer with a preferable thickness of about 20 μm, and comprises the inter...

third embodiment

[0125]In this embodiment, the need for impregnation is lessened by (partial) formation of the anode and the cathode earlier in the process. Therefore, the first component of the third embodiment contains the anode material in the electrode layer. The first component is sintered under reducing conditions, after which a sealing layer 6 and / or contact layer 8 and a cathode layer are deposited. The cathode layer is preferably about 30 μm thick.

[0126]The second component of the third embodiment does not contain an electrode layer. After sintering, a sealing layer 6 and contact layer 8 are deposited.

[0127]The stack is assembled by stacking the first and second components in an alternate order, and sealing / bonding them at a low temperature of from about 600° C. to about 900° C., preferably of from about 650° C. to about 850° C.

[0128]In the third embodiment, the need for impregnation of the electrodes is considerably reduced. However, a catalyst may still be impregnated on the anode and / or ...

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Abstract

A reversible SOFC monolithic stack is provided which comprises: 1) a first component which comprises at least one porous metal containing layer (1) with a combined electrolyte and sealing layer on the porous metal containing layer (1); wherein the at least one porous metal containing layer (1) hosts an electrode; 2) a second component comprising at least one porous metal containing layer (1) with a combined interconnect and sealing layer on the porous metal containing layer; wherein the at least one porous metal containing layers hosts an electrode. Further provided is a method for preparing a reversible solid oxide fuel cell stack. The obtained solid oxide fuel cell stack has improved mechanical stability and high electrical performance, while the process for obtaining same is cost effective.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application is a divisional application of U.S. patent application Ser. No. 12 / 065,357, filed Apr. 23, 2008, which is a national stage filing under 35 U.S.C. 371 of International Application No. PCT / EP2006 / 008537, filed Aug. 31, 2006, which claims foreign priority to European Patent Application No. 05018912.5 filed Aug. 31, 2005, the disclosures of which are incorporated by reference herein in their entireties. Priority to each application is hereby claimed.BACKGROUND OF THE INVENTION[0002]The present invention relates to a reversible solid oxide fuel cell stack and a method for preparing same.[0003]Solid oxide fuel cells (SOFC's) are well known in the art and come in various designs. Typical configurations include a flat plate design and a tubular design, wherein an electrolyte layer is sandwiched between two electrodes. During operation, usually at a temperature from 500° C. to 1100° C., one electrode is in contact with oxyg...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): F02C1/00C25B9/18H01M8/10H01M8/24
CPCH01M4/861H01M4/8885H01M4/9033H01M4/905Y02E60/50H01M8/2435H01M2008/1293Y02E60/525H01M8/0276H01M8/243H01M8/2404H01M8/2483H01M8/2484Y02P70/50H01M8/02H01M8/12H01M8/24
InventorLARSEN, PETER HALVORSMITH, ANDERSMOGENSEN, MOGENSLINDEROTH, SOERENHENDRIKSEN, PETER VANG
OwnerDANMARKS TEKNISKE UNIV