Hexavalent ions insertion in garnet Li7La3Zr2O12 toward a low temperature densification reaction.

Nowadays, solid electrolytes are considered the main alternative to conventional flammable liquid electrolytes in lithium batteries. The fabrication of these materials is however limited by the strict synthesis conditions, requiring high temperature which can negatively impact the final performances. In this work, we report a modification of garnet based Li7La3Zr2O12 (LLZO) and show that the incorporation of tellurium can accelerate the synthesis process by lowering the formation temperature of cubic LLZO at temperature below 700°C. Optimized synthesis at 750 °C showed a decrease in particle size and cell parameter for samples with higher amounts of Te. The LLZO Te0.25 material shows an ionic conductivity of 5.15 × 10-5 S cm-1 after hot-pressing at 700 °C that is orders of magnitude higher than commercial compositions with Ta or Al undergoing the same densification conditions, and the highest value at this densification temperature. Partial segregation of Te-rich phases occurs for high temperature densification. Our study shows the advantages of Te insertion during the sintering process of LLZO garnet and demonstrates the achievement of highly ionically conductive LLZO with a low temperature treatment.