Solid oxide fuel cells (SOFCs) generate electrical power cleanly and efficiently; however, sluggish cathode (oxygen reduction reaction, ORR) kinetics require high operating temperatures (T op > 800°C) [2] Bulk oxygen ion transport depends strongly on the oxygen vacancy concentration and the energy barrier for an oxygen ion to migrate into an adjacent vacant site. Using first-principles density functional theory (DFT) and DFT+U calculations, Oxygen ion transport in perovskite-type (ABO 3 ) cathode materials depends on the material composition. We compare oxygen transport in La 1-x Sr x MO 3 (M=Cr,Mn,Fe,Co) to systematically analyze compositional effects. [4] Specifically, we study how Sr substitution alters the bulk structure, electronic properties, and oxygen vacancy formation energies of these materials. We also present oxygen migration pathways in LaCoO 3 and LaFeO 3 to understand the fundamental physics of the migration process. Our results provide insights for improving oxygen ion conductivities and guidelines for rationally designing new cathode materials. Finally, we show how structure-property relationships in Sr 2 Fe 1-x Mo x O 6 (SFMO), a promising cathode material, [7] We show that oxygen ion transport has a lower barrier in SFMO than in other MIEC cathodes, we explain the origins of this phenomenon, and we discuss how to optimize the Fe/Mo composition to obtain the best oxide ion conductivity
