In-situ surface chemical and structural self-reconstruction strategy enables high performance of Li-rich cathode

摘要

The critical challenges hindering the commercialization of Li-rich cathodes are their rapid-decaying capacity and voltage during cycling, originating from the degradation of lattice structure and interface side reaction between electrode and electrolyte. Surface engineering is considered to be an effective strategy to mitigate these disadvantages. Herein, an in-situ self-reconstruction strategy is proposed and developed to simultaneously optimize surface chemical composition and local structure of Li-rich cathodes. Specifically, the multifunction protective layer consisting of cation disorder phase and LiTMPO4-like (TM: Ni, Co, Mn) phase is produced by a simple PH3 gas treatment. LiTMPO4 featuring the ability against high potential is responsible for preventing interface side reaction and further reduce the dissolution of Mn. Both LiTMPO4-like phase and surface cation disorder phase contribute to stabilizing surface oxygen structure and limiting surface O-2 release. Compared to the pristine one, better integrity of chemical phases and higher oxidation state of TM cations after long-term cycling are confirmed in the modified sample by synchrotron-based scanning transmission X-ray microscopy, highlighting the key roles of the multifunction protective layer in stabilizing the capacity and voltage during cycling. This surface self-reconstruction strategy provides a new path for guiding the interface design of high energy density cathodes.