Lithiation-assisted exfoliation and reduction of SnS2 to SnS decorated on lithium-integrated graphene for efficient energy storage.

Low reversion of lithium sulfide and defects causing irreversible capacity loss are the primary causes of low Coulombic efficiency in tin sulfide/graphene-based composites. Herein, we synthesized a SnS/graphene composite via a novel lithiation-assisted exfoliation and reduction method using SnS2, n-butyllithium, and graphene oxide as raw materials. The experimental results reveal that lithium from the insertion agent combine with the oxygen-containing groups on graphene oxide; this can help in the reduction of hexagonal SnS2 to orthorhombic SnS during calcination and simultaneous pre-occupancy of the edge and defect sites of graphene; thus, additional lithium ion consumption during the initial several lithiation processes is diminished. Microstructural characterizations indicate that the exfoliated SnS nanosheets with a dramatically decreased lateral size (50-100 nm) are uniformly decorated on the surface of lithium-integrated graphene sheets. Consequently, the as-prepared SnS/graphene composite exhibits a significantly high SnS ultilization with a 77.5% initial Coulombic efficiency, which is the highest value reported in the current literature. Moreover, an excellent reversibility of conversion reaction (SnS + 2Li+ + 2e- ↔ Sn + Li2S) and a high reversible capacity of 1016.4 mA h g-1 after 100 cycles are expressed in this composite electrode, demonstrating its importance as an anode material for energy storage.