Nitrogen-doped carbon encapsulated in mesoporous TiO2 nanotubes for fast capacitive sodium storage

Controllable synthesis of insertion-type anode materials with beneficial micro- and nanostructures is a promising approach for the synthesis of sodium-ion storage devices with high-reactivity and excellent electrochemical performance. In this study, we developed a sacrificial-templating route to synthesize TiO2@N-doped carbon nanotubes (TiO2@NC-NTs) with excellent electrochemical performance. The as-prepared mesoporous TiO2@NC-NTs with tiny nanocrystals of anatase TiO2 wrapped in N-doped carbon layers showed a well-defined tube structure with a large specific surface area of 198 m(2) g(-1) and a large pore size of similar to 5 nm. The TiO2@NC-NTs delivered high reversible capacities of 158 mA h g(-1) at 2 C (1 C = 335 mA g(-1)) for 2200 cycles and 146 mA h g(-1) at 5 C for 4000 cycles, as well as an ultrahigh rate capability of up to 40 C with a capacity of 98 mA h g(-1). Even at a high current density of 10 C, a capacity of 138 mA h g(-1) could be delivered over 10,000 cycles. Thus, the synthesis of mesoporous TiO2@NC-NTs was demonstrated to be an efficient approach for developing electrode materials with high sodium storage and long cycle life. (C) 2020 Published by ELSEVIER B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.