In quest of cathode materials for Ca ion batteries: the CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni)

Abstract

Basic electrochemical characteristics of CaMO₃ perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni) as cathode materials for Ca ion batteries are investigated using first principles calculations at the Density Functional Theory level (DFT). Calculations have been performed within the Generalized Gradient Approximation (GGA) and GGA+U methodologies, and considering cubic and orthorhombic perovskite structures for Ca_xMO₃ (x = 0, 0.25, 0.5, 0.75 and 1). The analysis of the calculated voltage–composition profile and volume variations identifies CaMoO₃ as the most promising perovskite compound. It combines good electronic conductivity, moderate crystal structure modifications, and activity in the 2–3 V region with several intermediate Ca_xMoO₃ phases. However, we found too large barriers for Ca diffusion (around 2 eV) which are inherent to the perovskite structure. The CaMoO₃ perovskite was synthesized, characterized and electrochemically tested, and results confirmed the predicted trends.