Impact of Chemical Composition of Strontium-Doped Lanthanum Manganite Cathode on Microstructural Change and Performance During Long-Term Operation of SOFCs

Abstract

The cells composed of strontium-doped lanthanum manganite (LSM) cathode and yttria-stabilized zirconia (YSZ) electrolyte show time-dependent events, such as the performance enhancement and/or deterioration, under polarized states. In this study, the influence of LSM composition on the microstructure of LSM/YSZ interface as well as electrochemical properties during prolonged operation was investigated. LSM cathodes with three different compositions were used and the microstructural change was evaluated quantitatively by a focused ion beam–scanning electron microscope (FIB–SEM). It was clarified that for LSMs with A-site deficient compositions, the change in TPB-length had a minor contribution to the performance enhancement upon the initial cathodic current passage. Furthermore, after 100 h of discharge the thin layer of LSM was formed over YSZ electrolyte, accompanied with an increase in cathode overpotential. These phenomena are strongly correlated with the change in oxygen nonstoichiometry of LSM under polarized states.