Evaluation of Impurity Levels in Cathodes of Seven Different SOFC Stacks and Modules before and after Long-Term Operation

A national project on durability and reliability of SOFCs entitled "Fundamental Study on Rapid Evaluation Method of SOFC Durability" (FY 2013- 2017) focuses on a lifetime of 90,000 h with a degradation rate of 0.1 %/1,000 h. A total of 7 participating companies have been involved in the improvement of durability of SOFC cells/stacks. AIST, as a neutral research institute, is continuously carrying out dissectional analyses using secondary ion mass spectrometry (SIMS) of cell stacks from each stack manufacturer before and after long-term operation in order to clarify the cumulative effect on degradation of trace impurities, which would be difficult to detect using conventional analyses. In this paper, we evaluated impurity levels with focus on chromium and sulfur poisoning in cathodes of 7 different SOFC stacks and modules before and after long-term operation.