Ultrafast lithium storage in TiO2-bronze nanowires/N-doped graphene nanocomposites

A TiO2-bronze/N-doped graphene nanocomposite (TiO2-B/NG) is prepared by a facile hydrothermal combined with hydrazine monohydrate vapor reduction method. The material exhibits macro-and meso-porosity with a high specific surface area of 163.4 m(2) g(-1). X-Ray photoelectron spectroscopy confirms the successful doping of nitrogen in the graphene sheets. In addition, the TiO2-B nanowires are substantially bonded to the NG sheets. Cyclic voltammetry and electrochemical impedance spectroscopy show that the N-doped graphene improves the electron and Li ion transport in the electrode which results in better electrochemical kinetics than that of the pristine TiO2-B nanowires. As a result, the charge transfer resistance of the TiO2-B/NG electrode is significantly reduced. In addition, the lithium diffusion coefficient of TiO2-B/NG increases by about five times with respect to that of pristine TiO2-B. The TiO2-B/NG composite exhibits a remarkably enhanced electrochemical performance compared to that of TiO2-B. It shows a discharge capacity of 220.7 mA h g(-1) at the 10C rate with a capacity retention of 96% after 1000 cycles. In addition, it can deliver a discharge capacity of 101.6 mA h g(-1) at an ultra high rate of 100C, indicating its great potential for use in high power lithium ion batteries.