Effects of alkaline earth metal doping on garnet Li7La3Zr2O3

Abstract

The garnet Li7La3Zr2O12 (LLZO) has gained significant attention as a promising solid electrolytes for all-solid-state Li-ion batteries. However, the cubic phase of LLZO, which offers better ionic conductivity compared to the tetragonal phase, is thermodynamically unstable under ambient conditions. We synthesized and investigated ternary-doped LLZO to stabilize the cubic phase and enhance its ionic conductivity. The effects of doping on the crystal structure, microstructure, and ionic conductivity were characterized by various measurement techniques. The results reveal successful incorporation of the ternary-doped elements into the cubic garnet structure without formation of secondary phases. Specifically, the introduction of alkaline earth metals with increased ionic radius resulted in an expansion of the crystal lattice and enhanced microstructure. These beneficial effects of doping led to the highest ionic conductivity of 4.29 × 10-4 S cm−1 for Li6.45Ga0.133La2.95Ba0.05Zr1.8Ta0.2O12 with a relative density of 94.63%.

Keywords

• Solid state Li-ion electrolyte
• Garnet LLZO
• Ion conductivity
• Ternary-doping
• Alkaline earth doping