Oxygen deficient, carbon coated self-organized TiO2 nanotubes as anode material for Li-ion intercalation

Abstract

Since several years, research for high capacity anode materials in Li-ion batteries is addressed to titanium dioxide (TiO₂), which offers important advantages in terms of cost effectiveness, safety and environmental compatibility. This work reports on the lithiation and delithiation characteristics of anodically grown, self-organized TiO₂ nanotubes annealed in Ar (TiO_2−x) and Ar/C₂H₂ (TiO_2−x–C). The systems are used as model composite electrodes for the anode in Li-ion batteries. Anatase TiO_2−x–C nanotubes demonstrate a superior Li storage capacity as high as 320(±68) mA h g⁻¹ (Li_0.96TiO₂) compared to 180(±38) mA h g⁻¹ (Li_0.54TiO₂) for TiO_2−x. This is comparable to the highest reported capacities for TiO₂ nanotubes to date. The double layer capacities are estimated from cyclic voltammetry measurements to 85 μF cm⁻² for TiO_2−x and 20 μF cm⁻² for TiO_2−x–C nanotubes respectively. Additionally, electrochemical impedance spectroscopy reveals smaller charge transfer resistances for TiO_2−x–C nanotubes at the solid/liquid interface which improves the transfer of Li⁺-ions from the electrolyte into the electrode.