Anatase TiO2 as a Na+-Storage Anode Active Material for Dual-Ion Batteries.

Anatase TiO2 used as the sodium-storage anode is coupled with a graphite cathode to construct dual-ion batteries. The batteries display wide voltage window (1.0-4.7 V), long cycling stability (98 mAh g-1 after 1400 cycles at 500 mA g-1), and considerable rate performance (102 mAh g-1 at 1500 mA g-1). Furthermore, the kinetic behaviors of Na+ and PF6- ions are investigated through electrochemical impedance spectroscopy, the galvanostatic intermittent titration technique, and the potentiostatic intermittent titration technique. The corresponding apparent ion diffusion coefficient is calculated, and the results indicate that the transport of PF6- anions in the graphite cathode is swift.