Improved Li-Ion conduction by ion-conductor Li1.5Al0.5Ge1.5(PO4)3 additive in garnet type Li7La3Zr2O12 solid electrolytes

In this study, Li1.5Al0.5Ge1.5(PO4)3 (LAGP) was introduced as a sintering aid up to 4 wt % into the garnet type Li7La3Zr2O12 (LLZO) structure. Results pointed out that increasing LAGP amount improved densification and electrochemical performance comparing with pure LLZO. But, LAGP addition facilitated the open pore formation and cracking occurred eventually. 1 wt % LAGP containing LLZO was optimized as they show the best electrolytic properties with 0.78 mS/cm ionic conductivity and 1.25 × 10−7 S/cm electronic conductivity without suffering from the open pore formation. LAGP added LLZO samples exhibited one of the lowest activation energies around 0.17 eV when compared to the pure LLZO (0.24 eV) as LAGP stayed between LLZO grains and maintain the continuous ion-conductive pathway. Considering all of the findings, the study offers a new approach to obtain bulk type LLZO solid electrolytes with the lowest activation energy thanks to the intergranular ion conduction. •A new approach to facilitate ion conduction is offered.•Low melting point Li + conductor Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is introduced.•LAGP amount increases the volume density and open pore volume.•LAGP addition shows a limited improvement on ionic conductivity.•The activation energy reduced by providing a continuous ion-conductive pathway.