Sodium-Ion Storage Properties of Thermally Stable Anatase

Anatase titanium dioxide (TiO 2 ) is a potential anode material for sodium-ion batteries (NIBs). However, the low electronic conductivity and sluggish ion diffusion kinetics at high rate hamper its practical applications. Herein, we demonstrate a sol-gel approach to the synthesis of thermally stable anatase nanoparticles with a carbon shell as anode materials for NIBs. A sample calcined at 750 °C (designated as H-750TiO 2 @C) exhibits high-rate capability and excellent stability against cycling with no capacity loss after 2000 cycles at 1 A g -1 . In situ X-ray diffraction and Raman spectroscopy characterization results reveal a nearly zero-strain characteristic of the anatase phase during charge/discharge processes. In situ transmission electron microscopy, ex situ X-ray photoelectron spectroscopy, and scanning electron microscope characterization results of samples collected at different charged and discharged states suggest that the anatase phase undergoes an irreversible sodiation-activation during the initial discharge process to form a sodiated-TiO 2 phase. A full cell assembled with H-750TiO 2 @C as the anode and Na 3 V 2 (PO 4 ) 3 as the cathode delivers an energy density of 220 Wh kg -1 , demonstrating H-750TiO 2 @C is a potential anode material for NIBs.