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Solid oxide fuel cell electrode systems and methods

Solid oxide fuel cell electrode systems and methods description/claims

The present disclosure relates generally to solid oxide fuel cells and, more particularly, to a metal-matrix or in situ composite for use as an interconnect in a solid oxide fuel cell.

Metallic plates used as interconnects between individual fuel cells of a solid oxide fuel cell can make the fuel cells quite heavy for aircraft flight applications. Interconnects may be made for example of stainless steel alloys. Solid oxide fuel cell systems fabricated from heavy gage, dense materials such as this are less attractive for long endurance aircraft propulsion applications because of their weight.

Stainless steel, while heavy, has other materials characteristics which make it suited for use in fuel cells. For example, stainless steel has resistance to hydrogen embrittlement (formation of hydrides), good resistance to oxidation,with fair creep strength and conductivity at temperatures above 800° C.

As a result, there is a need for a material to be used as a an interconnect in a solid oxide cell that has adequate structural and thermal/electrical conductivity characteristics at a lower weight than materials currently in use (such as stainless steel), while having adequate resistance to hydrogen embrittlement and oxidation.

In accordance with an embodiment of the present invention, a solid oxide fuel cell (SOFC) interconnect comprises a metal sheet with an air side and a fuel side. The metal sheet comprises a metallic composite having a matrix. The matrix comprises a first metal. The metal sheet also comprises a plurality of discontinuous, elongated, directional reinforcement wires. The reinforcement wires comprise a second metal that is immiscible in the first metal. An oxidation protection layer is disposed on the air side of the metal sheet.

In accordance with another embodiment, a solid oxide fuel cell (SOFC) comprises a plurality of individual fuel cells. Each individual fuel cell comprises an anode layer, a cathode layer, and a catalyst layer between the anode layer and the cathode layer. The SOFC also comprises a plurality of interconnects separating adjacent individual fuel cells. Each one of the plurality of interconnects comprises a metal sheet a metallic composite. The metallic composite has a matrix comprising copper or silver and a plurality of discontinuous, elongated, directional reinforcement wires dispersed in the matrix. The reinforcement wires comprise molybdenum.

In accordance with another embodiment, a method of fabricating an interconnect for a solid oxide fuel cell (SOFC), comprises melting a charge comprising copper and from 20 to 38 volume percent molybdenum and then cooling to form an ingot comprising a metallic composite. The metallic composite has a copper matrix and spheroids dispersed within the matrix. The method also includes forging the ingot followed by a first anneal to form a rough bar of metallic composite, swaging the rough bar followed by a second anneal to form a plurality of rods suitable for drawing, drawing the plurality of rods followed by a third anneal to form a plurality of wires of the metallic composite, bundling and canning to form a sheet of the metallic composite. The sheet is suitable for use as an interconnect in an SOFC.

The scope of the disclosure is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.

FIG. 1 shows a block diagram illustrating a detail of a portion of a solid oxide fuel cell in accordance with an embodiment.

FIG. 2 shows a cross-section of an interconnect of a solid oxide fuel cell in accordance with an embodiment.

FIG. 3 shows a flow diagram illustrating a method of fabricating a metal plate in accordance with an embodiment.

FIG. 4 shows a flow diagram illustrating a method of fabricating an interconnect for use in a solid oxide fuel cell.

FIGS. 5A, 5B and 5C show the thermal expansion coefficient, bulk thermal conductivity and RT electrical conductivity versus percent volume of molybdenum in a copper matrix in example embodiments.

FIG. 6 shows an interconnect of a solid oxide fuel cell in accordance with an embodiment.

• Provisional Patent
• Utility Patent

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