A facile post-process method to enhance crystallinity and electrochemical properties of SnO2/rGO composites with three-dimensional hierarchically porous structure

Abstract

In this work, three SnO₂/reduced graphene oxide (SnO₂/rGO) composites with a three-dimensional hierarchically porous structure were synthesized via freeze drying and different annealing temperatures in an air atmosphere. The results show that the crystallinity of SnO₂ can be improved with increasing annealing temperature in air atmosphere, but the crystallinity quality of rGO presents a volcanic type change with increasing annealing temperature. The cyclic voltammetry curves indicate that the reaction of Li⁺ intercalation into SnO₂ and rGO can only occur in the 120 °C sample, so that the cycling performance of the 120 °C sample is the best. Its initial discharge capacity is 1610 mA h g⁻¹ at current densities of 0.5 A g⁻¹. After 100 cycles, the specific discharge capacity is 429 mA h g⁻¹. The XPS results reveal that SnO₂ nanoparticles are anchored on the surface of rGO via Sn–O–C bonds. During the charge/discharge process, the volume expansion of SnO₂ nanoparticles can be prevented through enhancing the crystallinity of ultra-small SnO₂ nanoparticles (about 3.2 nm). This might pave the way for the commercial production of the SnO₂/rGO electrode because these post-processing technologies are more easily implemented in industrial production.