Constructing hierarchical hollow microspheres with Co9S8-modified CoS nanosheets for high-performance sodium storage

Transition metal sulfides have drawn increasing attention as anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their practical application is still hindered by the rapid decay of capacity and severe volume variation during cycling. Herein, we constructed a hollow microspheres material composed of Co₉S₈-modified CoS nanosheets with the heterostructured interface through a one-step solvothermal method. When applied as the anode for SIBs, CoS/Co₉S₈ exhibited a superior specific capacity of 600 mAh g⁻¹ after 100 cycles at 0.5 A g⁻¹, and a remarkable cycling performance of 456 mAh g⁻¹ after 1500 cycles at 5 A g⁻¹. The outstanding electrochemical performance can be owed to the unique three-dimensional hollow hierarchical structure, which can effectively alleviate volume expansion during cycling. Moreover, density functional theory calculation further verified the improved electronic conductivity and structural stability because of the CoS/Co₉S₈ heterostructure.