Cation-Disorder-Assisted Reversible Topotactic Phase Transition between Antifluorite and Rocksalt Toward High-Capacity Lithium-Ion Batteries
Hiroaki Kobayashi, Takashi Tsukasaki, Yoshiyuki Ogasawara, Mitsuhiro Hibino, Tetsuichi Kudo, Noritaka Mizuno, Itaru Honma, Kazuya Yamaguchi
Abstract
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 Li6CoO4 cathode. This cubic phase is synthesized by a simple mechanochemical treatment of conventionally prepared tetragonal Li6CoO4. It displays a reversible capacity of 487 mAh g–1, a high value because of a reversible three-electron reaction using Co2+/Co3+, Co3+/Co4+, and O2–/O22– redox, occurring without O2 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.