Preparation of Porous Zn_0.76Co_0.24S Yolk-Shell Microspheres with Enhanced Electrochemical Performance for Sodium Ion Batteries

Transition metal sulfides, due to excellent redox reversibility and considerable electronic conductivity, have been proposed as an available alternative material for rechargeable batteries. In this work, porous Zn_0.76Co_0.24S (ZCS) yolk-shell microspheres are favorably obtained through a facile solvothermal manner, followed by a vulcanization process. The effects of vulcanization temperature on the morphology, structure, and electrochemical performance of the products are also explored. Owing to the unique buffering space and generous active sites of yolk-shell structure, the electrode material exhibits excellent cycle and rate performance. Comparatively, Zn_0.76Co_0.24S vulcanized at 140 °C (ZCS-140) retains a capacity of 671 mAh g⁻¹ at 100 mA g⁻¹ after 100 cycles and delivered a reversible capacity of 389 mAh g⁻¹ at 1 A g⁻¹ after 1000 cycles with a decay of only 0.029 % per cycle, which is better than that of ZCS-120 and ZCS-160, indicating its potential to be a promising next-generation anode for SIBs.