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

Abstract

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 m² 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.