Improving the electrochemistry of anatase for sodium ion batteries by using self-organized TiO_2 nanotubes prepared by anodization under variable voltage

摘要

In order to prepare TiO_2 nanotubes of controlled morphology, anodization of titanium under fixed potential or under variable potential was used. Self-organized TiO_2 nanotubes with amorphous character are obtained, and after annealing at about 500°C in air atmosphere anatase-phase nanotubes are formed. The resulting areal capacity values in sodium cells are in the order of 1.0-1.5 mAh/cm~2, and after 600 discharge-charge cycles the gravimetric capacity vs. Na is about 200 mAh/g. Consequently, the electrochemical behavior of anatase in sodium cell can be competitive in comparison to the behavior in lithium cell. On the other hand, the use of aqueous electrolyte batteries may be an alternative. Using cyclic voltammetry, we have found that self-organized anatase nt-TiO_2 electrode in aqueous solution containing lithium (or sodium) ions exhibits reversible redox processes, particularly after optimization of the electrolyte and electrode properties (i.e. anodization of Ti under ramping of voltage).