Facile in-situ synthesis of heazlewoodite on nitrogen-doped reduced graphene oxide for enhanced sodium storage.

Nickel sulfide based anode materials, featuring rich types, high specific capacities and favorable conversion kinetics, have been proved to be promisingly applied in high-performance sodium-ion batteries (SIBs). Unfortunately, the poor electronic/ionic conductivity, together with the structure change induced degraded capacity upon cycling, restricts their further development. In this work, heazlewoodite nanoparticles decorated on nitrogen doped reduced graphene oxide (NiS/NrGO) were fabricated via a facile combined approach with freeze-drying and subsequent in-situ sulfidation. In the obtained hybrid structure, the synergistic effect between NiS and NrGO endows the composite with highly conductive pathways, thus accelerating the charge transfer. Benefitting from the buffering matrix offered by NrGO as well as the tight combination between NiS and NrGO, this novel NiS/NrGO demonstrates satisfying sodium storage performance, with a stable reversible capacity of 299.2 mAh g up to 100 cycles (0.1 A g) and a high initial Coulombic efficiency of 76.8%. Importantly, the rational structure design and synthesis method, as well as the insights on the improved electrochemical performance reported in this work, should be helpful for the development of new-type host materials with high performance for SIBs.