Nitrogen and Sulfur Dual-Doped Oxygen-Deficient TiO2/C Composites for Superior Sodium Storage Properties

Sodium-ion batteries (SIBs) have been considered as promising replacements to lithium-ion batteries (LIBs) for large-scale energy storage applications. For anode materials, titanium dioxide (TiO2) as a typical insertion-type anode material have been extensively investigated as a safety, stable, cheap and environmental-friendly anode materials for SIBs. Constructing suitable TiO2 crystal structure is a common modification strategy for improving the diffusion kinetics of sodium ion within TiO2 and its intrinsic electronic conductivity. Herein, a multi-atomic doped oxygen-deficient TiO2/C composites (N, S-NTC) was successfully synthesized with excellent electrochemical performance. Synergistic effect of N, S and Ni elements on the structure, morphology and electrochemical performance was investigated. Electron Paramagnetic Resonance (EPR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis indicated that the Ni, N, S doping can introduce oxygen deficiency, narrow the bandgap of TiO2 and facilitating Na+ diffusion, further providing higher electronic/ionic conductivities and faster electron transport channel. As a consequence, the anode materials delivered ultrahigh rate performance and cycling performance of a high reversible capacity of 128.6 mA h g(-1) at 1 A g(-1) after 3000th cycles.