Cost-Effective Highly Robust SOFC Interconnect Coating Process

Solid oxide fuel cells (SOFCs) offer exceptional promise for electrical power generation with reduced carbon footprint, but SOFC reliability must be improved for the technology to be widely commercialized. SOFCs utilize ferritic stainless steel sheets as interconnect plates between the fuel and air chambers. They are sealed using alkali earth containing silicate glass formulations that remain vitreous at the operating temperatures, typically 650-850C, to provide mechanical compliance. Reactivity of the alkali earth elements in the seal glass with chromium oxide in the steel interconnect leads to diffusion formed voids in the glass, which in turn cause seal failures. YSZ has been identified as a potential barrier to prevent alkai earths in the seal glass from reacting with the interconnect. To be successful, YSZ with a high degree of structural perfection and uniformity must be formed in an extremely cost effective way over rough interconnect surfaces. Sonatas approach will leverage atomic layer deposition (ALD) to form such a YSZ barrier layer. The technical objective is to demonstrate high integrity YSZ thin film barriers with high density and conformality, using a simple tooling/masking technique to permit very large production lot sizes of 1000-2000 interconnects per run with the barrier limited to the perimeter area of the interconnect. In Phase I, Sonata will demonstrate a novel ALD process to deposit YSZ barrier layers on ferritic stainless steel interconnects. Sonata will collaborate with FuelCell Energy to demonstrate feasibility of the barrier. Sonata will also perform a detailed cost analysis of the barrier layer production process. Commercial Applications and Other Benefits: Highly dense and conformal YSZ barrier films are expected to dramatically increase SOFC reliability, which will multiply the demand and applications of the technology, and leverage the expanding supply of natural gas and other fuels in the U.S. Once the technology is established, other thermal barrier applications may benefit from this technology, particularly for use in engines and turbines, leading to increased efficiency.