Preparation of binder-free thin film Li4Ti5O12 anode with an adjustable thickness through anodic TiO2 nanotubes

Binder-free thickness-controllable Li4Ti5O12 for application in lithium ion batteries was fabricated by the reaction of Li2CO3 and anodic nanotubular TiO2 at 800 °C. As the concentration of Li2CO3 increased, the thickness of Li4Ti5O12 film increased, leading to increase in discharge capacity. The Li4Ti5O12 film prepared at the optimized concentration of Li2CO3 of 3.8 × 10−6 mol displayed the maximum capacity of 104 μA h cm−2 at the first cycle, which corresponds to 103 mA h g−1. We found that excess Li2CO3 led to creation of LiTiO2 phases in the Li4Ti5O12 film, which reduced the discharge capacity. For comparison, a Li4Ti5O12 film was prepared by the reaction of Li2CO3 on a non-anodized Ti foil. In this case, discharge capacity was dramatically reduced due to the formation of Li2TiO3 phases in Li4Ti5O12, which was confirmed by TEM and XRD analysis.