Formation of defects in garnet-type solid-state electrolyte <b>Li7La3Zr2O12</b>

Abstract

The garnet-type solid-state electrolyte Li7La3Zr2O12 (LLZO) is one of the most promising candidates for solid-state batteries, particularly due to its high ionic conductivity in the cubic phase. Using ab initio density functional theory, in this study, we determined the structures and calculated the formation energies of a range of defects in the cubic phase of LLZO. We also performed detailed analysis of the properties of the defects. We found that the formation energy of a defect is predominantly influenced by the charge state and the chemical potentials (the growth conditions). Under O-poor and metal-rich conditions, oxygen vacancies in neutral and charged states, Li interstitials, Li(vacancy-interstitial) Frenkel-pair defects, and the Schottky-type defect are the most prevalent, while Li vacancies are the most favorable defects under O-rich and metal-poor conditions. Positively charged O and Zr vacancies, as well as La vacancies in both neutral and charged states, also become accessible at high Fermi levels. In addition, under Li-rich conditions, 2VLi + LaLi has relatively low formation energy. These findings underscore the importance of the chemical environment in shaping the defect landscape and consequently the ionic conductivity of cubic LLZO. The results obtained from this study are crucial for the development of more efficient and safer solid-state batteries, which could lead to significant advancements in energy storage technologies.