Current Status of Rapid Evaluation of Durability of Six SOFC Stacks within Nedo Project

Six solid oxide fuel cell stacks manufactured by Kyocera, MHPS, TOTO, NGK spark plug, NGK Insulator, Murata Manufacturing have been investigated to identify their performance degradation behavior, extract the major sources of degradation factors, clarify the degradation mechanism, and predict the time dependent contribution of such degradation to life time.  Stack performance was analyzed into several contributions, and an interesting correlation of overpotential values and ohmic loss has been obtained in addition to identification of respective degradation rates.  Respective degradation issues have been examined experimentally with SIMS, FIB-SEM, STEM and described as key simulation techniques to predict the long life up to 90,000 h.  Emphases have been placed on degradation of cathodes with Cr or S; to ensure the appropriateness for overcoming such poisoning effects, care is made to measure the impurity level after long term operation in various environments.  For simulation, focus was made to overcome some gaps between knowledge on stacks and on single (or buttons) cells appearing in several aspects.