Domain boundaries and their influence on Li migration in solid-state electrolyte (La,Li)TiO sub(3)

The influence of 90[degrees] domain boundaries in (La,Li)TiO sub(3) (LLTO) on the Li conduction mechanism has been examined by a combination of state-of-the-art electron microscopy techniques and first-principles calculations. The atomistic structure of 90[degrees] domain boundaries in LLTO was determined from aberration-corrected scanning transmission electron microscopy images. At 90[degrees] domain boundaries, each perovskite unit of one domain is connected by an La-rich layer to units of the neighboring domain. First-principles calculations of a model domain boundary show that Li migration through the La layer has a very high activation energy, E sub(a), of 3.58 eV, indicating that La layers serve to block Li migration. However, if La vacancies are present within La layers, the migration energy decreases significantly to 0.58 eV, a value more in line with experimental observation. The results show that Li conduction in LLTO is strongly influenced by 90[degrees] domain boundaries. The activation energy in a single crystal (E sub(a) = 0.19 eV) is much lower, suggesting that if 90[degrees] domain boundaries could be eliminated, an increase in conductivity of approximately three orders of magnitude compared with conventional LLTO could be achieved.