Fluorine-Doped SnO₂@Graphene Porous Composite for High Capacity Lithium-Ion Batteries

Abstract

For the first time, a composite of fluorine-doped SnO2 and reduced graphene oxide (F-SnO2@RGO) was synthesized using a cheap F-containing Sn source, Sn(BF4)2, through a hydrothermal process. X-ray photoelectron spectroscopy and X-ray diffraction results identified that F was doped in the unit cells of the SnO2 nanocrystals, instead of only on the surfaces of the nanoparticles. F doping of SnO2 led to more uniform and higher loading of the F-SnO2 nanoparticles on the surfaces of RGO sheets, as well as enhanced electron transportation and Li ion diffusion in the composite. As a result, the F-SnO2@RGO composite exhibited a remarkably high specific capacity (1277 mA h g–1 after 100 cycles), a long-term cycling stability, and excellent high-rate capacity at large charge/discharge current densities as anode material for lithium ion batteries. The outstanding performance of the F-SnO2@RGO composite electrode could be ascribed to the combined features of the composite electrode that dealt with both the electrode dynamics (enhanced electron transportation and Li ion diffusion due to F doping) and the electrode structure (uniform decoration of the F-SnO2 nanoparticles on the surfaces of RGO sheets and the three-dimensional porous structures of the F-SnO2@RGO composite).