Electronic Modulation of Oxygen Anion Intercalated Perovskite Oxides for Pseudocapacitance
Perovskite oxides have been recognized since 2014 as oxygen anion intercalation pseudocapacitive electrodes, a mechanism fundamentally distinct from bulk-diffusion-controlled battery redox. Pseudocapacitance in these materials arises from surface Faradaic reactions involving OH− adsorption, oxygen vacancy-mediated anion migration, and reversible transition metal valence changes (e.g., Mn2+→Mn3+→Mn4+ in LaMnO3±δ). The primary bottleneck is low energy density, compounded by a narrow voltage window (<0.5 V) due to water decomposition in 6 M KOH. This perspective examines the interplay of electronic structure—localized density of states near the Fermi level and spin-electron states—with OH− adsorption/desorption, oxygen ion mobility, conductivity, oxygen vacancy concentration, and interface reconfiguration. Hydroxyl metal oxide formation during cycling facilitates interface reconstruction, boosting capacity without foreign additives. Alternative electrolytes (organic, ionic liquid, Water-in-Salt) are proposed to widen the voltage window. The assembly of perovskite electrodes with suitable anodes into high-performance devices remains the ultimate goal. Key challenges persist in electrolyte selection, interface stability, and scalable manufacturing, necessitating deeper mechanistic understanding beyond empirical electrochemical performance.