Core‐Shell Se‐Doped TiO2@Carbon Nanotubes for High‐Performance Sodium‐Ion Batteries

Abstract

AbstractTitanium dioxide (TiO2) has been considered as a promising anode material for sodium‐ion batteries (SIBs), because of its abundance, safety and eco‐friendliness. However, the inferior electronic conductivity and low sodium ion diffusion rate of TiO2 hinder its improvement of electrochemical performance. To overcome these drawbacks, herein, core‐shell Se‐doped TiO2@carbon nanotubes (denoted as Se‐TiO2@CNTs) are successfully designed and fabricated, in which the TiO2 nanoparticle aggregated shells are conformally coated on the carbon nanotubes, while the metallic Se species are physically confined within the meso/micropores. When examined as a SIB anode, the Se‐TiO2@CNTs electrode demonstrates excellent sodium storage performance, correspondingly delivering high reversible capacities of 222.7/208.5 mA h g−1 after 200/1000 cycles at current densities of 0.2/1.0 A g−1, and even a capacity of 140.2 mA h g−1 after 4500 cycles at a high‐rate of 5.0 A g−1. The high reversible capacity, long‐term cycling stability, and high‐rate capability of the Se‐TiO2@CNTs can be owing to the unique structure characteristics, as the hollow/porous structure with high specific surface area of 335.4 m2 g−1 efficiently shortens the Na+ diffusion length and facilitates the electrolyte penetration, while Se‐doping and carbon supporting greatly enhance the electronic conductivity of the Se‐TiO2@CNTs electrode.