Cobalt-molybdenum binary metal sulfide wrapped by reduced graphene oxide for advanced sodium ion anode material

Abstract Substantial researches have been devoted to metal sulfides for developing anode materials of sodium ion batteries on account of the high theoretical capacity and high reaction activity. Nevertheless, the issue of volumetric variation impedes their development. Herein, a composite of cobalt-molybdenum binary metal sulfide wrapped by reduced graphene oxide (CoS2-MoS2@rGO) was synthesized by an annealing process and rGO wrapping using CoMoO4 as the precursor. The as-prepared CoS2-MoS2@rGO composite exhibits good cycling performance with 561.5 mA h g-1 at the 50th cycle at the current density of 0.2 A g-1 and rate capability of 382.2 mA h g-1 at 2 A g-1 for sodium ion batteries, which is attributed to the uniform coating of rGO to buffer the volumetric variation and maintain the structural integrity accompanied with improved ion diffusion and enhanced electrical conductivity.