Reversible Conversion Reaction of Tin Monosulfide/Graphene Nanocomposite As a Negative Electrode Material for Na-Ion Battery

To date, there has been much research on electrochemical study of lithium ion batteries. However, the question has also been raised for depletion of lithium resources, causing interest in sodium ion batteries. While extensive investigations on conversion reactions of various metal oxides as lithium electrode materials have been carried out, conversion reactions in sodium-based systems have been rarely reported. Here we have synthesized Tin monosulfide with graphene oxide nanocomposites by simple hydrothermal reaction and annealing for reduction of graphene oxide in successive process. The phase and morphology of SnS/rGO nanocomposites have been investigated by XRD, SEM, and TEM, respectively. The electrochemical performances of SnS/rGO nanocomposites were tested in sodium nonaqueous electrolytes. It delivers 588mAh/g at a rate of 50 mA/g, indicating relatively higher capacity compared to previous reports. This material also shows stable capacity retention with 396mAh/g at 100mA/g after 100cycles. Furthermore, we conduct ex-situ XRD measurements on the initial stage of cycles to investigate the structural differences during the conversion reactions in sodium system. Finally, we demonstrate which electrochemical reaction has directly affected on the cause of capacity fading during cycles.