Simple and Large Scale Synthesis of SnSX Nano-Belts, Flowers and Sheets for Li-Ion Battery Anode Applications

In this report, a variety of nanostructured materials of SnS_x (such as nanobelts, nanoflowers and interconnected nanosheets) were prepared by hydrothermal synthesis method using mercaptopropionic acid (MPA) as the structure directing agent. By simply adjusting the amount of MPA in the precursor formulations and heating period, nanobelts, nanoflowers and interconnected nanosheets of SnS_x were obtained. The detailed growth processes of SnS₂/SnS nanoflowers from nanobelts are elucidated. Morphological evolution of the definitively shaped SnS_x nanostructures was followed by scanning electron microscopy. X-ray diffraction (XRD) analyses confirmed an orthorhombic crystal structure for SnS nanobelts. The XRD patterns of SnS_x nanoflowers and interconnected nanosheets show a mixed phase comprising an orthorhombic crystal structure of SnS coupled with a hexagonal crystal structure of SnS₂. The SnS_x nanostructured materials demonstrated extremely large capacities when used as Li-ion battery anodes. Among the various anode nanostructures that we studied, the anode based on SnS₂/SnS interconnected nanosheets showed an exceptionally high capacity. Initially it showed a reversible capacity of 800 mAh g^-1 at a current density of 100 mA g^-1 and even after 50 cycles it retained a capacity of 470 mAh g^-1 with almost 97% Coulombic efficiency. The SnS₂/SnS interconnected nanosheets also exhibited an excellent rate capability even at a very high current density (1160 mA g-1) a charge capacity of 360 mAh g^-1 was obtained.  We demonstrate that this facile hydrothermal route assisted by MPA adopted herein for the development of SnS_x based high performance anodes is also extendable to other potential inorganic anode materials.