Ultrathin Nanosheets Assembled Hierarchical Co/NiS_<i>x</i>@C Hollow Spheres for Reversible Lithium Storage

Abstract

Cobalt sulfides are good candidate anode materials for lithium ion storage for their high theoretical capacities. However, their electrochemical performance is restricted by their volume change during the cycles, leading to a sharp capacity fading in the subsequent process. To overcome these disadvantages, ultrathin nanosheets assembled hierarchical cobalt sulfides@C hollow spheres are fabricated by a hydrothermal and subsequent carbon enwrapping strategy. The as-prepared hierarchical Co₉S₈@C hollow spheres deliver an enhanced electrochemical performance with both long-term cyclability and reversible specific capacities. 823 mA h g^–1 reversible capacity could be maintained after 200 cycles at a current density of 100 mA g^–1. More importantly, the present synthesis strategy shows good generality for the synthesis of nickel sulfide and Ni–Co bimetal sulfides hollow spheres with improved performance in anode materials of lithium ion batteries