Fuel cell stack having foil interconnects and laminated spacers

Abstract

Interconnects and perimeter spacers for a fuel cell stack are provided as flexible elements which can conform to non-planarities in a stack's electrolyte elements and thereby avoid inducing torsional stresses in the electrolyte elements. The interconnects are foil elements about 0.005 inches thick, formed of a superalloy such as Hastelloy, Haynes 230, or a stainless steel. The perimeter spacers comprise a plurality of laminate thin spacer elements, each thin spacer element being a laminate of superalloy and a “soft” material such as copper, nickel, or mica. The spacer elements can slide past one another; thus the perimeter spacers can be physically thick, to form the gas flow spaces within the stack, while also being torsionally flexible.

Description

TECHNICAL FIELD [0001] The present invention relates to fuel cells; more particularly, to stacks comprising a plurality of individual cells being both physically separated and electrically connected by interconnect elements; and most particularly, to such a fuel cell stack wherein the interconnect elements are thin foils and the spacers are laminates of foils formed alternately of superalloy and a compliant material. BACKGROUND OF THE INVENTION [0002] Fuel cells which generate electric current by controllably combining elemental hydrogen and oxygen are well known. In one form of such a fuel cell, an anodic layer and a cathodic layer are separated by a permeable electrolyte formed of a ceramic solid oxide. Such a fuel cell is known in the art as a “solid oxide fuel cell” (SOFC). Either pure hydrogen or reformate is flowed along the outer surface of the anode and diffuses into the anode. Oxygen, typically from air, is flowed along the outer surface of the cathode and diffuses into the...

AI Technical Summary

Benefits of technology

The patent describes a way to make interconnects and perimeter spacers for fuel cell stacks that can adapt to the uneven surfaces of the stack's elements. The interconnects are thin foil elements made of a superalloy or stainless steel, while the thick perimeter spacers are made of a combination of a superalloy and a flexible soft material like copper or mica. These spacers can slide past each other, creating gas flow spaces and also allowing for flexibility in torsion. The technical effect of this invention is to improve the performance and flexibility of fuel cell stacks by making the interconnects and spacers more adaptable to the uneven surfaces of the stack's elements.

Problems solved by technology

One problem encountered in prior art fuel cell stacks is that they are relatively bulky and heavy.

Another problem encountered in some prior art fuel cell stacks involves the brittleness of the ceramic oxide electrolyte elements.

Such a fuel cell is said to be “anode-supported.” The ceramic oxide electrolyte elements, which extend to the edges of the stack in contact with the anodes, typically are not optically flat and are also quite brittle.

Prior art perimeter spacers, being monolithic, cannot twist to accommodate non-planarities in the electrolyte elements and anodes, so that sealing between the non-flat surfaces becomes difficult.

Also, because of the non-flat surfaces, an electrolyte element may be cracked during assembly of the stack.

In either case, failure of the stack can occur.

Avoiding these problems by finishing the electrolyte elements to be optically flat is cost-prohibitive.

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