Preferentially Oriented TiO2 Nanotubes as Anode Material for Li-Ion Batteries: Insight into Li-Ion Storage and Lithiation Kinetics.

Self-organized TiO2 nanotubes (NTs) with a preferential orientation along the [001] direction are anodically grown by controlling the water content in the fluoride-containing electrolyte. The intrinsic kinetic and thermodynamic properties of the Li intercalation process in the preferentially oriented (PO) TiO2 NTs and in a randomly oriented (RO) TiO2 NT reference are determined by combining complementary electrochemical methods, including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic cycling. PO TiO2 NTs demonstrate an enhanced performance as anode material in Li-ion batteries due to faster interfacial Li insertion/extraction kinetics. It is shown that the thermodynamic properties, which describe the ability of the host material to intercalate Li ions, have a negligible influence on the superior performance of PO NTs. This work presents a straightforward approach for gaining important insight into the influence of the crystallographic orientation on lithiation/delithiation characteristics of nanostructured TiO2 based anode materials for Li-ion batteries. The introduced methodology has high potential for the evaluation of battery materials in terms of their lithiation/delithiation thermodynamics and kinetics in general.