Strain-Enhanced Oxygen Dynamics and Redox Reversibility in Topotactic SrCoO_3-δ (0 < δ ≤ 0.5)

Oxide materials facilitating high-ion mobility and fast-ion transport are highly sought after for applications requiring intensive redox cycling. Some of these materials, in addition, may exhibit interesting multifunctional properties originating from electron correlation such as magnetism and metal–insulator transitions. SrCoO 3-δ (SCO) is one such compound, which recently has attracted a lot of interest due to its ability of taking on and releasing oxygen fluently. Here we investigate thoroughly the dynamics of oxygen vacancies and redox cycles in SCO under broad epitaxial strain conditions (−1.2% ≤ η ≤ +3.9%). We show that the capacity of this material to act as an “oxygen sponge” depends strongly on the strain conditions, with moderate strains of ca. +2% providing the optimal conditions for reversible redox cycling. First-principles simulation methods are employed to understand the experimental trends observed for SCO reduction in vacuum, and to provide microscopic insight into the formation of oxygen vacancies. Our work demonstrates that strain engineering can serve as an efficient means to control the dynamics of oxygen anions and redox reversibility in topotactic materials.