Report of Five-year NEDO Project on Durability/Reliability of SOFC Stacks

The five-year NEDO project on the durability / reliability of SOFC stacks ended on March 2013. Final results are reported with emphases on correlation between fabrication sequence and degraded parts and on effects of operation conditions such as temperature, overpotential of electrodes etc. NEDO targets on durability and reliability were successfully achieved at the end of project. Summary of detailed analyses on respective degradations found in those SOFC stacks involved is given to clarify common and individual features of degradations. Chemical and electrochemical natures of interactions of electrodes with gaseous impurities are successfully identified, whereas reliability of electrolytes is found to be strongly governed by electrochemical features. Detailed investigations on microstructure and its change revealed several stages for relations between performance degradation and microstructural changes. Reliability of cell assemblies are well treated by a combination of approaches on fundamental mechanical properties, modeling of electrochemical reactions and stress analyses with a focus on the volume change caused by the valence changes in electrolyte, interconnect and electrodes.