Synchronous Tailoring Surface Structure and Chemical Composition of Li-Rich-Layered Oxide for High-Energy Lithium-Ion Batteries

Li-rich-layered oxide is considered to be one of the most promising cathode materials for high-energy lithium ion batteries. However, it suffers from poor rate capability, capacity loss, and voltage decay upon cycling that limits its utilization in practical applications. Surface properties of Li-rich-layered oxide play a critical role in the function of batteries. Herein, a novel and successful strategy for synchronous tailoring surface structure and chemical composition of Li-rich-layered oxide is proposed. Poor nickel content on the surface of carbonate precursor is initially prepared by a facile treatment of NH3 center dot H2O, which can retain at a certain low amount on the surface in the final lithiated Li-rich-layered oxide after a solid-phase reaction process. Moreover, a phase-gradient outer layer with layered-coexisting phase-spinel structure toward to the outside surface is self-induced and formed synchronously based on poor nickel surface of the precursor. Electrochemical tests reveal this unique surface enables excellent cycling stability, improved rate capability, and slight voltage decay of cathodes. The finding here sheds light on a universal principle both for masterly tailoring surface structure and chemical composition at the same time for improving electrochemical performance of electrode materials.