Achieving Superior Electrochemical Performance of Li-Rich Cathode Materials with a Uniform Li4Mn5O12@PDA-Li2SO4 Coating Layer by a One-Step Approach

Li-rich Mn-rich layered oxides (LLOs) are considered key cathode candidates for next-generation lithium-ion batteries (LIBs) because of their high specific capacity that owes to the anionic redox. However, the poor cycling performance, low initial Coulombic efficiency, and unsatisfactory rate performance of LLOs hinder their practical application. Herein, a uniform multifunctional Layered@Li4Mn5O12@PDA-Li2SO4 coating layer is constructed on the surface of a Li-rich material by a simple one-step process. By constructing a zero-strain Li4Mn5O12 spinel with more Mn4+ on the particle surface, the Jahn-Teller effect and the resulting manganese dissolution can be avoided. PDA provides a chemical protective layer that can reduce the growth of an undesirable cathode electrolyte interphase and also promotes the rapid ion migration of electrons/ions. This coating layer can significantly improve the initial Coulombic efficiency (ICE), rate performances, and cycling stability of the material. The as-prepared LLO exhibits a greatly strengthened specific capacity of 270.2 mAh/g with an enhanced ICE of 83.38% and long-term cyclability of 79.14% retention after 500 cycles. The as-prepared LLO's discharge specific capacity at 10C is 131 mAh/g, whereas the pristine LLO only has 93 mAh/g. This study elucidates the mechanism of the composite surface structure and establishes the relationship between lithium-ion interfacial conductivity and electrochemical performance, offering a strategy for near-surface design of LLOs in high-energy-density LIBs.