In Situ-Formed Hollow Cobalt Sulfide Wrapped by Reduced Graphene Oxide as an Anode for High-Performance Lithium-Ion Batteries

Transition-metal sulfides have been considered as promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical specific capacity and superior electrochemical performance. However, the large volume change during the discharge/charge process causes structural pulverization, resulting in rapid capacity decline and the loss of active materials. Herein, we report Co1–xS hollow spheres formed by in situ growth on reduced graphene oxide layers. When evaluated as an anode material for LIBs, it delivers a specific capacity of 969.8 mAh·g–1 with a high Coulombic efficiency of 96.49% after 90 cycles. Furthermore, a high reversible capacity of 527.2 mAh·g–1 after the 107th cycle at a current density of 2.5 A g–1 is still achieved. The results illustrate that in situ growth on the graphene layers can enhance conductivity and restrain volume expansion of cobalt sulfide compared with ex situ growth.