Mixed-valence Mn–Co oxide nanoshells anchored on reduced graphene oxide nanosheets for enhanced lithium storage kinetics and cycling stability

A hierarchical cobalt-doped manganese oxide/reduced graphene oxide hollow nanoshell (rGO/MCO-NS) composite was developed as a high-performance anode for lithium-ion batteries. This architecture effectively integrates cobalt doping with confinement by rGO nanosheets to overcome the inherently poor electrical conductivity and significant volume changes of manganese oxide anodes. X-ray absorption spectroscopy analyses elucidated the local atomic coordination and oxidation states, confirming that cobalt incorporation and thermal reduction result in a mixed-valence Mn²⁺/Mn³⁺ and Co²⁺ lattice with abundant oxygen vacancies. Owing to this tailored nanostructure, the rGO/MCO-NS anode exhibits significantly better lithium storage performance than its undoped and rGO-free counterparts, delivering a high reversible capacity, exceptional cycling stability, and enhanced rate capability. Electrochemical tests revealed a predominantly pseudocapacitive charge-storage mechanism, improved charge-transfer kinetics, and a unique cycling-induced activation phenomenon that increases capacity during prolonged cycling periods. In summary, this study demonstrates a powerful strategy that leverages both doping and nanoconfinement for the development of next-generation anodes with enhanced lithium storage performance and excellent long-term durability.