Lithium- and Manganese-Rich Oxide Cathode Materials for High-Energy Lithium Ion Batteries

Layered lithium- and manganese-rich oxides (LMROs), described as xLi2MnO3·(1–x)LiMO2 or Li1+yM1–yO2 (M = Mn, Ni, Co, etc., 0 < x <1, 0 < y ≤ 0.33), have attracted much attention as cathode materials for lithium ion batteries in recent years. They exhibit very promising capacities, up to above 300 mA h g−1, due to transition metal redox reactions and unconventional oxygen anion redox reaction. However, they suffer from structural degradation and severe voltage fade (i.e., decreasing energy storage) upon cycling, which are plaguing their practical application. Thus, this review will aim to describe the pristine structure, high-capacity mechanisms and structure evolutions of LMROs. Also, recent progress associated with understanding and mitigating the voltage decay of LMROs will be discussed. Several approaches to solve this problem, such as adjusting cycling voltage window and chemical composition, optimizing synthesis strategy, controlling morphology, doping, surface modification, constructing core-shell and layered-spinel hetero structures, are described in detail