Nickel sulfide nanospheres anchored on reduced graphene oxide in situ doped with sulfur as a high performance anode for sodium-ion batteries

NiSx-rGOS is prepared via a facile and cost effective hydrothermal process, with the structure of ultrafine NiSx nanospheres uniformly wrapped in the in situ S-doped rGO matrix. The uniform nanostructural NiSx and high conductivity of S-doped rGO (rGOS) can effectively increase the ionic and electronic conductivity of the NiSx-rGOS composite, thus resulting in high capacity utilization of the active materials. Moreover, the buffering layer provided by the rGOS matrix can accommodate the volume change of the NiSx and protect the nanoparticles from aggregation during the repeated cycling process. The as-prepared NiSx-rGOS composite demonstrates a high reversible capacity of 516 mA h g(-1) at 0.2 A g(-1) with a capacity retention of 96.8% over 100 cycles and a remarkable rate performance of 414 mA h g(-1) at 4 A g(-1), possibly exhibiting the best electrochemical performances of nickel sulfide for sodium-ion batteries.