Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, part I: Test fixture, sealing, and electrochemical performance

• A generic stack fixture was successfully demonstrated in a 3-cell stack at 800 °C.
• Cell, seal system, interconnect plate, and electrodes were presented.
• Electrochemical performance of LSM-based cell over 6000 h was reported.
• LSM-based cell showed low degradation rate of 1–2% per 1000 h.
• Post-mortem analysis was conducted and cause of sealing failure was identified.

A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing under realistic conditions. A NiO–YSZ anode-supported YSZ electrolyte cell with a composite cathode was used to evaluate the long-term stability of a sealing system, alumina coating, Ce-modified (Mn,Co)-spinel coating, ferritic stainles steel AISI441 interconnect metal, and current collectors. A 3-cell short stack was assembled and tested in constant current mode for 6000 h at 800 °C. Part I of the work addresses the stack fixture design, cell components, sealing system, cell performance, and post-mortem analysis. Parts II and III will discuss microstructure evolution, interfacial reactions, and degradation mechanisms. During 6000 h of testing, the top cell showed very low degradation (∼1.4% kh−1), while the middle and bottom cells exhibited much higher degradation after ∼2000 h. The rapid cell degradation was correlated to the open circuit voltage measurements and was attributed to glass seal failure, probably due to unbalanced stress conditions. Post-mortem analysis showed a characteristic yellowish color around the glass seal, suggesting formation of SrCrO4. Overall the developed stack test fixture was demonstrated as a simple and useful tool for evaluation of SOFC candidate materials in realistic conditions.