Heterostructured NiS2@SnS2 hollow spheres as superior high-rate and durable anodes for sodium-ion batteries

Tin-based sulfides have attracted increasing attention as anodes for sodium-ion batteries (SIBs) owing to their high theoretical capacity; however, the poor rate capability and inferior cycling stability caused by the low electrical conductivity, sluggish kinetics and drastic volume variations during cycling have greatly hampered their practical applications. Herein, heterostructured NiS2@SnS2 hybrid spheres were delicately designed and constructed by anchoring interconnected SnS2 nanosheets on metal-organic frameworks (MOFs)-derived NiS2 hollow spheres coupled with N-doped carbon skeleton through facile solvothermal and sulfurization/carbonization processes. The unique hollow heterostructure with highly conductive carbon matrix can effectively facilitate the charge transfer kinetics and ensure the desired buffer space while endowing more active sites and enhanced structural integrity, as demonstrated by the experimental and density functional theory (DFT) results. Benefitting from these merits, the NiS2@SnS2 hybrid composite displays a high reversible capacity of 820 mAh g−1 after 250 cycles at 1 A g−1, and retains a value of 673 mAh g−1 after 1,300 cycles at 5 A g−1, manifesting the excellent high-rate and durable sodium storage behaviors when applied in SIBs. This study shall shed more light on the fabricating and interface engineering of other transition metal based composite anodes for high performance SIBs.