Universal solid-state oxygen redox in antifluorite lithium oxides via transition metal doping

Solid-state oxygen redox can potentially be used in high-capacity cathode materials of lithium-ion batteries. This study demonstrates a reversible solid-state oxygen redox in antifluorite lithium oxide via doping of Ni. Ni-Doping of Li2O enables the reversible redox reaction of O2-/O22- in addition to the transition metal redox, with a reversible capacity of 270 mA h g-1. The O K-edge X-ray absorption spectroscopy reveals that the solid-state oxygen redox reaction is universal in transition metal dopants, which are probably activated by the 2p electron holes in O that are formed via hybridization with d orbitals of the transition metal. Considering the cathode performances and earth abundance of dopant transition metals, Ni-doping of Li2O effectively leads to the development of high-capacity cathode materials.