Ceramic interconnect for fuel cell stacks

Abstract

A fuel cell comprises a plurality of sub-cells, each sub-cell including a first electrode in fluid communication with a source of oxygen gas, a second electrode in fluid communication with a source of a fuel gas, and a solid electrolyte between the first electrode and the second electrode. The sub-cells are connected with each other with an interconnect. The interconnect includes a first layer in contact with the first electrode of each cell, and a second layer in contact with the second electrode of each cell. The first layer includes a (La,Mn)Sr-titanate based perovskite represented by the empirical formula of La_ySr_(1−y)Ti_(1−x)Mn_xO_b. In one embodiment, the second layer includes a (Nb,Y)Sr-titanate perovskite represented by the empirical formula of Sr_{(1−1.5z−0.5k±δ)}Y_zNb_kTi_(1−k)O_d. In another embodiment, the interconnect has a thickness of between about 10 μm and about 100 μm, and the second layer of the interconnect includes a (La)Sr-titanate based perovskite represented by the empirical formula of Sr_(1−z±δ)La_zTiO_d.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 063,643, filed on Feb. 5, 2008 and U.S. Provisional Application No. 61 / 009,003, filed on Dec. 21, 2007. The entire teachings of the above applications are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]A fuel cell is a device that generates electricity by a chemical reaction. Among various fuel cells, solid oxide fuel cells use a hard, ceramic compound of metal (e.g., calcium or zirconium) oxide as an electrolyte. Typically, in the solid oxide fuel cells, an oxygen gas, such as O2, is reduced to oxygen ions (O2−) at the cathode, and a fuel gas, such as hydrogen gas (H2) gas, is oxidized with the oxygen ions to form water at the anode.[0003]Interconnects are one of the critical issues limiting commercialization of solid oxide fuel cells. Currently, most companies and researchers working with planar cells are using coated metal interconnects. While metal interconnect...

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Benefits of technology

[0009]This invention has many advantages. Bi-layer ceramic interconnects of the invention meet all the major requirements for solid oxide fuel cell (SOFC) stack interconnects. (La,Mn)Sr-titanate based perovskite is stable and its electrical conductivity is high in an oxidizing atmosphere, and therefore this material can be used on the air side in the bi-layer ceramic interconnect. (Nb,Y)Sr-titanate based perovskite and (La)Sr-titanate based perovskite is stable and its electrical conductivity is high in a reducing atmosphere, and therefore this material can be used on the fuel side in the bi-layer ceramic interconnect. These materials also have the advantage that, containing no chromium, they do not have the problems associated with lanthanum chromites (LaCrO3). The present invention can be used in a solid ox

Problems solved by technology

Interconnects are one of the critical issues limiting commercialization of solid oxide fuel cells.

While metal interconnects are relatively easy to fabricate and process, they generally suffer from high power degradation rates (e.g. 10%/1,000 h) partly due to formation of metal oxides, such as Cr2O3, at an interconnect-anode/cathode interface during operation.

However, lanthanum chrom

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