Three birds with one stone: Reducing gases manipulate surface reconstruction of Li-rich Mn-based oxide cathodes for high-energy lithium-ion batteries

Abstract

Energy storage through additional anionic redox can deliver ultrahigh specific capacities of Lithium-rich manganese-based oxides cathode materials (LRMO). The commercial application of LRMO is hampered by several drawbacks, including structure degradation, continuous capacity and voltage decay, sluggish kinetics and severe irreversible oxygen release, stemming from generation of O₂ⁿ⁻ (0 ≤ n < 2) species during deep oxidation. Notably, relying solely on a single modification strategy only partially address the problems of LRMO materials. Herein, one-step phosphatizing-assisted interface engineering strategy was successfully implemented, simultaneously fabricating oxygen vacancies, spinel-like structure and an ionic conductor Li₃PO₄ capping layer on the surface. Among them, the formation of oxygen vacancies is accompanied by the production of a spinel phase buffer layer, which inhibits the generation of O–O dimers and oxygen loss, contributing to the stability and reversibility of anionic redox reactions. The lithium ions conductive protective layer of Li₃PO₄ accelerates Li⁺ diffusion rate while suppressing harmful interfacial side-reactions between the electrode and electrolyte. More importantly, the incorporation of P into the subsurface lattice regulates the local electron configuration and activates oxygen redox. As a result, the modification LRMO demonstrates an impressive reversible capacity of 312.9 mAh g⁻¹, with excellent capacity retention of 91.87 % at 1 C and 82.43 % at 2 C after 500 cycles, respectively. The mult-ianionic redox mechanism provides an effective and straightforward method to stabilizing LRMO for next-generation high-energy lithium-ion batteries.