Co₉S₈/MoS₂ Yolk–Shell Spheres for Advanced Li/Na Storage

A facile approach to synthesize cobalt sulfide/molybdenum disulfide (Co₉S₈/MoS₂) yolk-shell spheres was studied. Uniform sized CoMo-precursor spheres were prepared by a hydrothermal process. Subsequently, the CoMo-precursor spheres were successfully converted into yolk-shell structures via a sulfuration reaction in the presence of thioacetamide. During this step, the S₂ generated from the thioacetamide will react with the metal ions at elevated temperature. Finally, the Co₉S₈/MoS₂ yolk–shell spheres are obtained by a thermal annealing treatment at 700°C for 2 h in Ar/H₂ atmosphere. The structure and morphology of the CoMo-precursor spheres are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After the sulfurization process, the CoMo-precursor spheres can be converted to the Co-Mo-S yolk–shell structures with rougher surface. The sample possesses good electrochemical properties benefiting from the merits of both components. Such structures exhibit excellent Li/Na storage properties with high specific capacities, excellent rate capabilities and good cycling stability.