Triple-layered sandwich nanotube of carbon nanotube@TiO2 nanocrystalline@carbon with superior lithium storage performance

The triple-layered sandwich nanotube of carbon nanotube@TiO₂ nanocrystalline@carbon is synthesized. TiO₂ nanocrystalline stably adheres to carbon nanotubes. A layer of amorphous carbon shell derived by PPy tightly attaches on the surface of TiO₂ nanocrystalline. Carbon nanotube@TiO₂ nanocrystalline@carbon is of abundant mesopores, showing high pore volume of 0.92 cm³ g⁻¹ and large specific surface area of 612 m² g⁻¹. As anode material of lithium ion batteries, it exhibits high discharge capacity, desirable cycling performance (236 mA h g⁻¹ at 1C after 500 cycles) and excellent rate capability (187 mA h g⁻¹ at 10C). The outstanding lithium storage performance comes from the supporting effect of the internal carbon nanotube and the protecting effect of the external carbon shell, which significantly increase cycling stability and electronic conductivity of TiO₂. The large specific surface area brings about intense pseudocapacitive lithium storage effect, enhancing reversible capacity and rate performance of TiO₂.