SOFC INTERCONNECT DEVELOPMENT

Abstract

An interconnect for an SOFC stack is used to connect fuel cells into a stack. SOFC stacks are expected to run for 40,000 hours and 10 thermal cycles for the stationary application and 10,000 hours and 7000 thermal cycles for the transportation application. The interconnect of a stack must be economical and robust enough to survive the SOFC stack operation temperature of 750 C and must maintain the electrical connection to the fuel cells throughout the lifetime and under thermal cycling conditions. Ferritic and austenitic stainless steels, and nickel-based superalloys were investigated as possible interconnect materials for solid oxide fuel cell (SOFC) stacks. The alloys were thermally cycled in air and in a wet nitrogen-argon-hydrogen (N2-Ar-H2-H2O) atmosphere. Thermogravimetry was used to determine the parabolic oxidation rate constants of the alloys in both atmospheres. The area-specific resistance of the oxide scale and metal substrates were measured using a two-probe technique with platinum contacts. The study identifies two new interconnect designs which can be used with both bonded and compressive stack sealing mechanisms. The new interconnect designs offer a solution to chromium vaporization, which can lead to degradation of some (chromium-sensitive) SOFC cathodes.