A Unique Gradiently-Distorted O3-type Configuration for High-Performance Li-Rich Layered Oxides by...

Novel structures/configurations are highly desired to promote oxygen anionic redox chemistry in Li-rich layered oxides (LLOs) which however are hardly achieved by conventional near-equilibrium approaches. Herein, we propose a strategy of electrochemically driven ion (Li and Na)-exchange doping (EDIED) and subsequent annealing (EDIEDA) for creating new configurations in LLOs. The EDIEDA process enables an inwardly decreasingly distorted Na⁺-doped O3-type structure in the subsurface and a spinel phase at the surface, accompanied by radially gradient and circumferentially homogenous distribution of Na⁺. The distorted O3-type configuration can effectively mitigate the migration of transition metals (TMs) to improve the oxygen anionic redox reversibility by modulating the lower Hubbard band and the unhybridized O 2p orbitals. This leads to the capacities of 303 mAh g^-1 at 0.1C and 240 mAh g^-1 at 1 C for 2.0-4.6 V. This strategy can create new configurations for promising performance improvement which is also very effective for other layered oxides.