Acceleration tests: Degradation of anode-supported planar solid oxide fuel cells at elevated operating temperatures

As the solid oxide fuel cell (SOFC) technology matures, durability under real operating conditions is considered as one of the most critical issues for commercialization. The severe conditions encountered in practical operation include a large temperature gradient and generation of local hot spots within stacks. Herein, we report the degradation mechanisms of anode-supported planar SOFCs supplied by Posco Energy at elevated operating temperatures. A simple comparison of the voltage reduction rates at different operating temperatures does not appropriately represent the degree of degradation, because the rapid deterioration of the cell components at high temperatures is compensated for by the fast reaction and transport kinetics. A combination of impedance interpretation and post-mortem analysis reveals the major degradation processes that are distinctively accelerated by increasing temperature, including the chemical interaction between the cathode and electrolyte, the enlargement of the interfacial pores, the coarsening of the fine particles in the composite electrodes, the formation of interfacial cracks and Cr poisoning. Systematic analysis presented in this study provides guidelines for counteracting the unexpected temperature increase, and the database established under various extreme conditions would form the groundwork for achieving the lifetime goals of commercial SOFC systems.