Electrochemical Investigations on TiO₂-B Nanowires as a Promising High Capacity Anode for Sodium-ion Batteries

We report the electrochemical behaviors of TiO₂-B nanowire electrodes exhibiting a high operating potential where they can avoid severe Na plating and a de-sodiation capacity of 196 mAh g^-1, which is the highest among several types of titanium oxides reported for sodium ion batteries. When TiO₂-B nanowires are used as negative electrodes for sodium ion batteries, 1 mole of the TiO₂-B nanowire can take up approximately 1 mole of sodium ions during the sodiation process and reversibly relieve 0.6 mole of intercalated sodium during the subsequent de-sodiation process. It has been proved that TiO₂-B nanowire electrodes participate in a reversible single-phase Na insertion/desertion reaction during charge and discharge. The electrodes exhibit irreversible capacity, owing to electrolyte decomposition and residual irreversible Na insertion, as determined via in situ XRD, ICP, FE-SEM, XPS, and electrochemical analyses. Further, TiO₂-B is a superior material exhibiting long and stable cyclability with a specific capacity of 150 mAh g^-1 over 50 cycles.