Structural insights on understanding the cubic phase stabilization mechanism of sol-gel synthesized Li7-3xAlxLa3Zr2O12 (x= 0–0.4)–The effect of ZrOCl2 and ZrO (NO3) 2

Stabilization of cubic Li7La3Zr2O12 phase, one of the most promising solid electrolytes for Li-ion batteries, has been extensively studied in terms of various stabilizer additions in solution-based systems. However, different dissociation behavior of precursors on the cubic LLZO phase stabilization has not been studied. In this study, we offer an understanding for the stabilization of cubic Li7La3Zr2O12 phase by using ZrOCl2 and ZrO(NO3)2, which are having different dissociation behavior, with 0–40 mol% Al addition. After calcination at 1000 °C for 6 h, cubic phase is stabilized starting from 20 mol% Al content when ZrOCl2 was used, whereas tetragonal Li7La3Zr2O12 obtained for all Al contents when ZrO(NO3)2 was used. The highest ionic conductivity is obtained in the 30 mol% Al containing sample produced with the use of ZrOCl2. In the case of ZrOCl2 precursor, due to the higher tendency of Zr–O bond formation after dissociation, the cubic Li7La3Zr2O12 phase is stabilized. On the other hand, the presence of nitrate ions within solution hinders the cubic phase formation of Li7La3Zr2O12.