Sandwich-like CNTs/Si/C nanotubes as high performance anode materials for lithium-ion batteries

Co-axial silicon-coated carbon nanotubes (CNTs/Si) were successfully synthesized via a hydrothermal method. Sandwich-like carbon-coated CNTs/Si were obtained by an additional carbon coating. The as-prepared materials show superior cycling performance as anode materials in lithium ion batteries with a current density as high as 500 mA g^-1 with no observable structural changes during the charge/discharge process. In addition, stable reversible discharge capacities as high as 1508.5 mA h g^-1 after 1000 cycles were obtained. At higher current densities of 1 A g^-1 and 2 A g^-1, the CNTs/Si/C nanotubes also showed ideal cycling performance with reversible discharge capacities of 1216.6 mA h g^-1 and 932.2 mA h g^-1, respectively. The sandwich-like hollow tube structure of CNTs/Si/C not only alleviates the volume change during cycling, but also facilitates Li-ion and electron transport, and stabilizes the SEI layer. These results suggest that sandwich-like CNTs/Si/C nanotubes are a promising anode material for lithium ion batteries.