Nanocrystalline tin compounds/graphene nanocomposite electrodes as anode for lithium-ion battery

Nanocrystalline tin (Sn) compounds such as SnO2, SnS2, SnS, and graphene nanocomposites were prepared using hydrothermal method. The X-ray diffraction (XRD) pattern of the prepared nanocomposite reveals the presence of tetragonal SnO2, hexagonal SnS2, and orthorhombic SnS crystalline structure in the SnO2/graphene nanosheets (GNS), SnS2/GNS, and SnS/GNS nanocomposites, respectively. Raman spectroscopic studies of the nanocomposites confirm the existence of graphene in the nanocomposites. The transmission electron microscopy (TEM) images of the nanocomposites revealed the formation of homogeneous nanocrystalline SnO2, SnS2, and SnS particle. The weight ratio of graphene and Sn compound in the nanocomposite was estimated using thermogravimetric (TG) analysis. The cyclic voltammetry experiment shows the irreversible formation of Li2O and Li2S, and reversible lithium-ion (Li-ion) storage in Sn and GNS. The charge-discharge profile of the nanocomposite electrodes indicates the high capacity for the Li-ion storage, and the cycling study indicates the fast capacity fading due to the poor electrical conductivity of the nanocomposite electrodes. Hence, the ratio of Sn compounds (SnO2) and GNS have been altered. Among the examined SnO2:GNS nanocomposites ratios (35:65, 50:50, and 80:20), the nanocomposite 50:50wt% shows high Li-ion storage capacity (400 mAh/g after 25 cycles) and good cyclability. Thus, it is necessary to modify GNS and Sn compound composition in the nanocomposite to achieve good cyclability.