Vertical growth of nickel sulfide nanosheets on graphene oxide for advanced sodium-ion storage.

Sodium-ion batteries (SIBs) have attracted widespread attention as future energy storage systems. However, the development of advanced anodes for SIBs still lags far behind. Metal sulfides exhibit high theoretical capacity yet suffer from low rate-capability and limited life span, resulted from their poor electric conductivity, volumetric fluctuation, and polysulfide dissolution and shuttling. Herein, a two-dimensional (2D) vertical aligned nickel sulfide nanosheets grown uniformly on reduced graphene oxide (rGO) is designed. The unique 2D on 2D structure enhances the electrolyte/electrode contact and reduces the migration/diffusion path of electrons/Na+, thereby greatly improving the rate-performance. Besides, the rGO provides sufficient surface area to absorb polysulfides, which effectively mitigates the shuttling of the intermediates. The NiS@rGO composite delivers 360 mAh/g after 800 cycles at 5 A/g, and a capacity of 540 mAh/g is maintained after 100 cycles at 0.1 A/g. In-situ XRD diffraction confirmed the reversible transformation between NiS and Ni during cycling. Furthermore, when coupled with the well-developed Na 3 V 2 (PO 4) 3 @C (NVP@C) cathode, the NiS@rGO/NVP@C full cell achieves a stable discharge capacity of around 200 mAh/g. [Display omitted] [ABSTRACT FROM AUTHOR]