Comparison of perovskite and perovskite derivatives for use in anion-based pseudocapacitor applications

Abstract

The electrochemical behavior of perovskite oxides utilizing calcium and manganese along with their Ruddlesden–Popper (RP) counterparts are evaluated as anion intercalation-based pseudocapacitors by cyclic voltammetry and galvanostatic charging/discharging in 1 M KOH. We find that higher oxygen vacancy contents (δ) achieved by annealing in a reducing atmosphere leads to greater charge storage capacities. Additionally, we demonstrate how the governing descriptor for pseudocapacitive performance shifts from the number of oxygen vacancies and surface redox sites at high scan rates to facile oxygen diffusion and the ability to store oxide anions within interstitial sites of the rock salt layers in the RP materials at low scan rates. Both the perovskite and RP materials are evaluated as two-electrode asymmetric pseudocapacitors utilizing SrFeO_2.5 as the anode material. The cell containing SrFeO_2.5//Ca₂MnO_4−δ performed the best with a high energy density of 73 W h kg⁻¹ at a power density of 530 W kg⁻¹.