Superstructure Control of Anionic Redox Behavior in Manganese-Based Cathode Materials for Li-Ion Batteries.

Abstract

Anionic charge compensation creates conditions for realizing high capacity and energy density of Li-ion batteries cathode materials. However, the issues of voltage hysteresis, capacity attenuation, and structure transformation caused by the labile anionic redox are still difficult to solve fundamentally. The superstructure formed by a Li-Mn ordered arrangement is the intrinsic reason to trigger the anionic charge compensation. In this work, manganese-based cathode materials with series of Li-Mn ordered superstructure types have been prepared by an ion exchange method, and superstructure control of the anionic redox behavior has been synthetically investigated. With the dispersion of a LiMn6 superstructure unit, the aggregation of Li vacancies in Mn slab is gradually inhibited, which eliminates the production of O-O dimers and improves the reversibility of oxygen redox. Therefore, the voltage hysteresis and capacity fading have been significantly improved. Meanwhile, the amount of reactive oxygen species and their capacity contribution is reduced, and the sluggish electrochemical reaction kinetics of anion requires a low current density to boost the high-capacity advantage. This paper provides effective ideas for the design of various superstructures and the rational utilization of anionic redox.