Fig. 1. Schematic changes of anatase TiO2 upon lithiation.

The schematic bulk lattice structures of (a, b) pristine and lithiated TiO₂. Insets in a and b are the typical TiO₆ unit cells without and with the distortion, which leads to asymmetric Ti-O bonds and generates a dipole moment as presented by the arrow in b. c Schematic of the band bending and driving force in the TiO₂ and Li-TiO₂ bulks without and with the lattice distortions induced dipole moments, respectively. The band bending and driving force exists only in surface layer of TiO₂ but in both surface layer and bulk of Li-TiO₂.