Characterization of TiO2 thin films prepared by electrolytic deposition for lithium ion battery anodes

The electrolytic deposition of TiO2 thin films on platinum for lithium batteries is carried out in TiCl4 alcoholic solution and the films are subsequently annealed. The as-prepared films are amorphous TiO(OH)2·H2O, transformed into anatase TiO2 at 350 °C, and then gradually into rutile TiO2 at 500 °C. Cyclic voltammograms show oxidation and reduction peaks at 2.20 and 1.61 V, respectively, corresponding to charge and discharge plateaus at 1.98 and 1.75 V vs. Li+/Li. The specific capacity decreases with increasing current density for film of 128-nm thickness in the initial discharge. It is observed that the diffusion flux of Li+ insertion/extraction into/from TiO2 controls the reaction rate at higher current densities. Consequently, at low film thickness, high discharge capacity (per weight) is found for the initial cycle at a current density of 10 μA cm−2. However, the capacity of prepared films in various thicknesses approach 103 ± 5 mAh g−1 after 50 cycles, since the formation of cracks for thicker films offers shorter diffusion paths for Li+. In addition, TiO2 films show electrochromic properties during lithiation and delithiation. - Highlights: ► TiO2 films have been prepared by electrolytic deposition for Li ion batteries. ► The capacity decreased with increasing film thickness at higher current density. ► TiO2 films showed electrochromic properties during lithiation and delithiation.