Low-temperature surfactant-free synthesis of tin oxide-reduced graphene oxide nanocomposites and their textural property-dependent lithium storage characteristics

Tin oxide-graphene composite has emerged as a promising material for numerous applications such as energy storage. In the present work, we report one-pot low-temperature (95 °C) surfactant-free synthesis of tin oxide-reduced graphene oxide (rGO) nanocomposites by varying graphene oxide (GO) to tin (II) 2-ethylhexanoate weight ratio (R = 0.00, 0.02, 0.06, 0.12). X-ray diffraction and electron microscopy measurements confirm the existence of nanocrystalline tetragonal SnO₂ (size, ~3.0 nm), decorated on rGO sheets. Also, FTIR spectral study of the samples is performed to understand the chemical bond vibrations in the nanocomposites. Relative structural defects in rGO of nanocomposites are analyzed by Raman spectroscopy. The chemical reactions possibly proceed via oxidation of Sn²⁺ used as tin precursor, forming SnO₂ with the simultaneous reduction of GO to rGO. Multipoint BET nitrogen adsorption–desorption isotherm analysis shows that the specific surface area increases with R value but external surface area related to mesoporosity (pore diameter, ~3 nm) initially increases, reaches a maximum at R = 0.06 and then decreases for further increase in the R in the samples. On increasing R value, the trend of change of 1st cycle Coulombic efficiency is found to be identical with the change of external surface area of the samples. At R = 0.06, the sample demonstrates a reversible lithium storage capacity of 626 mAhg⁻¹ (80 % of theoretical capacity) with good cyclability, signifying the positive effect on the structural defects and also in the textural property of the materials. This study can be adopted for other metal oxide semiconductor–rGO nanocomposites for energy storage application.

SnO₂–rGO nanocomposites for improved lithium storage characteristics