Suppression of O-redox reactions by multivalent Cr in Li-excess M0.8M0.8ʹO4 (M,Mʹ = Cr, Mn, and Ti) cathodes with layered and cation-disordered rock-salt structures

Abstract We study cathode properties of Li-excess Li 2.4 M 0.8 M 0.8 ′ O4 (M, M'= Cr, Mn, and Ti) materials with layered and cation-disordered rock-salt structures by first-principles calculations. Results show that, as Li-removal amounts y increase in Li 2.4 − y M 0.8 M 0.8 ′ O4, local structures at a certain amount of cation sites change from octahedral to tetrahedral coordinations with O especially at Cr sites. Calculated voltage–capacity curves are consistent with experimental results, and it is found that Cr-redox reactions predominate in whole y ranges for (M, M') = (Cr, Mn) and (Cr, Ti), while Mn-redox and O-redox at low and high y regions, respectively, are dominated for (M, M') = (Mn, Ti). In the cathode materials with Cr, both O-redox and O2-release reactions are found to be suppressed by multivalent Cr.