Construction of triple-layered sandwich nanotubes of carbon@mesoporous TiO2 nanocrystalline@carbon as high-performance anode materials for lithium-ion batteries

Triple-layered sandwich nanotubes of carbon@mesoporous TiO 2 nanocrystalline@carbon were prepared through coating hydrous titania and resorcinol-formaldehyde resin on carbon nanotubes followed by controllable crystallization and carbonization . Material characterization indicated that TiO 2 nanocrystalline with the size of 5–6 nm was uniformly assembled to the mesoporous sandwich layer of carbon nanotube-in-nanotube, leading to large specific surface area of 465.4 m 2  g −1 and large pore volume of 0.695 ml g −1 . As anode material for lithium ion batteries , triple-layered sandwich nanotubes exhibited high lithium storage capacity (244 mAh g −1 at 0.1C), good rate capability (115 mAh g −1 at 5C), and excellent cycling stability (191 mAh g −1 with coulombic efficiency of 100.2% was retained after 200 cycles at 0.2C, presenting 79% of capacity retention ratio). The superior lithium storage properties should be attributed to synergistic superiorities of TiO 2 nanocrystalline, the mesoporous sandwich layer structure and carbon nanotube-in-nanotube. These unique structural characteristics effectively reduce Li + diffusion length; enhances intercalation storage capability and pseudocapacitive interfacial storage capability of TiO 2 ; provides sufficient space to accommodate volume variation of TiO 2 nanocrystalline; increases electron conductivity and structure stability of TiO 2 . It is anticipated that the present triple-layered sandwich nanotube provides a unique carbon-based hybrid structure for other energy storage materials.