C-Doped TiO2-B Nanowires Derived from TiC As an Anode Materials for Lithium Ion Batteries with High Rate Performance

Abstract

In the recent past nanostructured materials have been attracting much interest owing to their physical and chemical characteristics, which make them extremely suitable for a number of applications. In particular, one of the most promising applications is their use as electrode materials for rechargeable lithium ion batteries (LIB)1-2. Among the anode materials, Titanium dioxide (TiO2) has been deeply investigated for lithium intercalation/de-intercalation due to high rate capability, very good reversible capacity, low volume expansion ( <2% ) upon cycling and furthermore lost cost, high abundant and very safe lithium reaction potential ~ 1.5 V vs Li/Li+, owing to these characteristics, TiO2 anodes have been considered to target in EVs and HEVs application1-3. Recently, the various polymorphs of TiO2 (anatase, rutle, brookite and bronze) have been explored as efficient anodes for LIB3. In particular, TiO2-Bronze (TiO2-B) has been receiving significant interest due to its theoretical capacity of 335 mAh g-1. Importantly, TiO2-B manifests the major advantages of fast charging-discharging through a pseudo-capacitive mechanism in addition to the bulk diffusion, whereas other polymorphs of TiO2 mostly show intercalation of Li-ion through bulk diffusion controlled mechanism3. However, the low electronic conductivity and low rate of Li-ion diffusivity of TiO2 are key issues for a high rate capable anode. To overcome these issues, we report synthesis of carbon-doped TiO2-B nanowires by facile and inexpensive method without using external carbon source. The carbon doping was verified by UV–visible and X-ray photoelectron spectroscopy and further structure and morphology was investigated with X-ray diffraction, Raman spectroscopy and Scanning and Transmission microscopies. The electrochemical performances of the C doped and undoped TiO2-B nanowires were tested by galvanostatic charge/discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. This novel C-doped materials presented high capacities and higher rate capability in electrochemical cycling experiments with respective to undoped material. This is attributed to the reduction of Li-ion diffusion path lengths along with improving electrical conductivity of TiO2-B nanowires. The electrochemical experiments demonstrated that C-TiO2-B nanowires electrodes exhibited superior lithium storage capacity of ~306 mAh g-1 at current rate of 0.1C as well as excellent rate ability of ~160 mAh g-1even at high current rate of 10C after 1000 cycle in lithium-ion batteries.