Enhancing electrochemical performance of lithium-ion battery anodes using hollow nanospheres with rich oxygen vacancies

Hollow Co/CoO@NSCO nanospheres were synthesized via solvothermal derivation from dual-ligand Co-MOF, followed by controlled calcination. The calcination-temperature-mediated tuning of Co/CoO ratios and oxygen vacancy concentrations significantly enhanced lithium storage performance. Optimized Co-450 (450 °C calcination) delivered exceptional reversible capacities of 1112.5 mAh g −1 at 0.2 A g −1 after 100 cycles and 605.6 mAh g −1 at 1 A g −1 after 1000 cycles. Ex situ XRD confirmed metallic Co's role as an electrochemically inactive conductive matrix, while oxygen vacancies (65.7 % by XPS) facilitated rapid Li + diffusion. Kinetic analysis revealed hybrid charge storage: capacitive effects (68 % contribution at 1 mV s −1 ) dominated by pseudocapacitance from Co 2+ /Co 3+ redox couples, complemented by diffusion-controlled processes. The hierarchical hollow structure accommodated volume changes, and heteroatom-doped carbon enhanced electronic conductivity. This work demonstrates calcination-driven phase engineering as a viable strategy for high-performance anodes.