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

Benefiting from the unique structure of ultrafine NiS_x nanospheres uniformly wrapped in the in situ S-doped rGO matrix, the NiS_x–rGOS electrode delivers a high reversible capacity of 516 mA h g⁻¹ at 0.2 A g⁻¹ and a remarkable rate performance of 414 mA h g⁻¹ at 4 A g⁻¹, offering a low cost and high performance anode material for Na-ion batteries.