Preparation of carbon-coated TiO2 nanostructures for lithium-ion batteries

Highlights: → We prepare carbon-coated TiO2 nanotubes/nanowires by one-pot hydrothermal method. → Carbon coating increases electronic conductivity at higher calcination temperatures. → Carbon coating suppresses the agglomeration of nanotubes at lower calcination temperatures. - Abstract: Carbon-coated TiO2 one-dimensional nanostructures are synthesized by hydrothermal reaction followed by post-calcination at various temperatures. Post-calcination induces crystallization of TiO2 and the complete crystallization of anatase phase is observed at 600 deg. C of the calcination temperature. Carbon-coated TiO2 nanostructures show relatively poor crystallinity as compared with the pristine counterparts, but their lithiation capacity and high rate capability are improved throughout all calcination temperatures. The coated carbon suppresses severe agglomeration of TiO2 nanotubes which allows easy access of Li-ions and electrons to the whole surface of primary nanotubes, leading to the better lithiation performance. Higher calcination temperatures cause excessive growth of nanotube walls, leading to the collapse of tubular morphology and deterioration of lithiation performance. At 700 deg. C of the calcination temperature, the enhanced electronic conductivity from the graphitization of the coated carbon seems to be the main reason for the improved capacity of TiO2 nanowires.