Significant role of oxygen redox reaction with O2-release in Li-excess cation-disordered rock-salt cathodes Li2+2xMn1−xTi1−xO4: First-principles calculations

Abstract

Cation-disordered rock-salt oxides Li2+2xMn1−xTi1−xO4 with Li-excess x are promising Li-ion battery cathodes employing the anion-redox strategy. To clarify cathode properties including cation and anion redox reactions with O2-releases, first-principles calculations are performed for Li2+2xMn1−xTi1−xO4 with x ranging from 0 to 0.3. Effects of x on voltage-capacity curves and electronic structures are discussed, showing that Mn-redox reactions predominate in early charging processes. As charging reactions further proceed, O-redox reactions contribute to the cathode reactions more significantly for higher x. O atoms tend to be released from the cathodes especially in late charging processes with a trend of easier O2-release for higher x, possibly accounting for lower experimental capacities than theoretical values.