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 TiO2 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 TiO2 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 TiO2; provides sufficient space to accommodate volume variation of TiO2 nanocrystalline; increases electron conductivity and structure stability of TiO2. It is anticipated that the present triple-layered sandwich nanotube provides a unique carbon-based hybrid structure for other energy storage materials. (C) 2019 Elsevier Ltd. All rights reserved.