A Li-rich layered oxide cathode with negligible voltage decay

With high capacity at low cost, Li- and Mn-rich (LMR) layered oxides are a promising class of cathodes for next-generation Li-ion batteries. However, substantial voltage decay during cycling, due to the unstable Li2MnO3 honeycomb structure, is still an obstacle to their practical deployment. Here we report a Co-free LMR Li-ion battery cathode with negligible voltage decay. The material has a composite structure consisting of layered LiTMO2 and various stacked Li2MnO3 components, where transition metal (TM) ions that reside in the Li layers of Li2MnO3 form caps to strengthen the stability of the honeycomb structure. This capped-honeycomb structure is persistent after high-voltage cycling and prevents TM migration and oxygen loss as shown by experimental and computational results. This work demonstrates that the long-standing voltage decay problem in LMRs can be effectively mitigated by internally pinning the honeycomb structure, which opens an avenue to developing next-generation high-energy cathode materials.