Surface coating can suppress side reactions between electrode and electrolyte in Lithium-Ion Batteries (LIBs) but may also affect the Li mobility when shuttling into / out from the electrode of a LIB. Lanthanum Oxide (La2O3) coating has been experimentally shown to enhance LIB performance. In this study, we investigate the diffusion of Li in pristine La2O3 to understand the enhanced electrochemical performance of several La2O3-coated Li-ion battery cathodes. We used Density Functional Theory (DFT) with Climbing Image Nudged Elastic Band (CI-NEB) to calculate the energy barrier and the diffusivity of Li. We considered three pathways, i.e., the octahedral-to-octahedral path (O-O), octahedral-tetrahedral-octahedral path (O-T-O), and octahedral-tetrahedral-tetrahedral-octahedral path (O-T-T-O), and our results suggest that the O-O pathway has the lowest Li energy barrier of 0.09 eV. This finding suggests that Li will preferably diffuse along the [010] direction. Furthermore, we find that Li will diffuse more slowly along the [001] direction.