Cation-Disorder-Assisted Reversible Topotactic Phase Transition between Antifluorite and Rocksalt Toward High-Capacity Lithium-Ion Batteries

Multielectron reaction electrode materials using partial oxygen redox can be potentially used as cathodes in lithium-ion batteries, as they offer numerous advantages, including high reversible capacity and energy density and low cost. Here, a reversible three-electron reaction is demonstrated utilizing topotactic phase transition between antifluorite and rocksalt in a cation-disordered antifluorite-type cubic Li 6 CoO 4 cathode. This cubic phase is synthesized by a simple mechanochemical treatment of conventionally prepared tetragonal Li 6 CoO 4 . It displays a reversible capacity of 487 mAh g –1, a high value because of a reversible three-electron reaction using Co 2+ /Co 3+, Co 3+ /Co 4+, and O 2– /O 2 2– redox, occurring without O 2 gas evolution. The mechanochemical treatment is assumed to reduce its lattice distortion by cation-disordering and facilitate a reversible topotactic phase transition between antifluorite and rocksalt structures via a dynamic cation pushing mechanism.