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

• TiO2-B nanowire exhibits high discharge capacity of 196 mAh g−1.
• TiO2-B nanowire presents long cycleability of 150 mAh g−1 at 50th cycle.
• 1 mole of TiO2-B can uptake 1 mole of Na+ during the initial charge.
• Only 60% of intercalated Na+ in TiO2-B can be deserted during the 1st discharge.
• Good surface electrolyte interface successfully forms after the 1st cycle.

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.