Graphene oxide oxidizes stannous ions to synthesize tin sulfide–graphene nanocomposites with small crystal size for high performance lithium ion batteries

Abstract

This study reports a novel strategy of preparing graphene composites by employing graphene oxide as precursor and oxidizer. It is demonstrated that graphene oxide can oxidize stannous ions to form SnS₂ and is simultaneously reduced to graphene, directly resulting in the formation of SnS_x–graphene (1 < x < 2) nanocomposites. The particle size of SnS_x in the nanocomposites is tailored to be about 5 nm, which is much smaller than that obtained in a previous study. As anodic materials for lithium ion batteries, SnS_x–graphene nanocomposites retain a discharge capacity of 860 mA h g⁻¹ after 150 cycles at a charge–discharge rate of 0.2 C, higher than the theoretical capacities of SnS₂ (645 mA h g⁻¹) and SnS (782 mA h g⁻¹) based on the traditional mechanism. A possible new mechanism, that Li₂S arising from tin sulfide in the first discharge cycle could be reversibly decomposed at a low potential to storage lithium, is proposed based on experimental results to explain the excellent properties of SnS_x–graphene nanocomposites.