A Sn–SnS–C nanocomposite as anode host materials for Na-ion batteries

A Sn–SnS–C nanocomposite is prepared by simply mechanically ball-milling Sn, SnS and C powders. In this composite, Sn nanocrystals are surface-coated with SnS nanoparticles and uniformly dispersed in the carbon matrix. During discharge, the SnS particles undergo an electrochemical conversion reaction to generate Sn and Na2S nanocrystals and then the Sn particles alloy with Na to produce the NaSn alloy. The conversion reaction of SnS and the alloying reaction of Sn with Na are completely reversible, producing a very high reversible Na-storage capacity of >600 mA h g−1 at an appropriate low potential of ∼0.7 V. Since the SnS phase provides an effective buffering matrix to alleviate the volumetric change of the Sn particles during Na insertion and extraction, and also serves as a separator to prevent the aggregation of the Sn nanoparticles, the Sn–SnS–C composite anode demonstrates a very good cycling stability with 87% capacity retention over 150 cycles, possibly usable for Na-ion batteries.