Robust S-doped TiO2@N,S-codoped carbon nanotube arrays as free-binder anodes for efficient sodium storage

Abstract

Titanium dioxide (TiO2) has been investigated broadly as a stable, safe, and cheap anode material for sodium-ion batteries in recent years. However, the poor electronic conductivity and inherent sluggish sodium ion diffusion hinder its practical applications. Herein, a self-template and in situ vulcanization strategy is developed to synthesize self-supported hybrid nanotube arrays composed of nitrogen/sulfur-codoped carbon coated sulfur-doped TiO2 nanotubes (S-TiO2@NS-C) starting from H2Ti2O5·H2O nanoarrays. The S-TiO2@NS-C composite with one-dimensional nano-sized subunits integrates several merits. Specifically, sulfur doping strongly improves the Na+ storage ability of TiO2@C-N nanotubes by narrowing the bandgap of original TiO2. Originating from the nanoarrays structures built from hollow nanotubes, carbon layer and sulfur doping, the sluggish Na+ insertion/extraction kinetics is effectively improved and the volume variation of the electrode material is significantly alleviated. As a result, the S-TiO2@NS-C nanoarrays present efficient sodium storage properties. The greatly improved sodium storage performances of S-TiO2@NS-C nanoarrays confirm the importance of rational engineering and synthesis of hollow array architectures with higher complexity.