Effects of alkaline earth metal elements and their synergistic roles with Ta for Li7La3Zr2O12

Abstract

Effects of alkaline earth metal elements and their synergistic roles with Ta for the modified Li7La3Zr2O12 (LLZO) are discussed. Li7.1La3Zr1.95M0.05O12 (M = Mg, Ca, Sr, Ba) with the substitution of alkaline earth metal ions for Zr4+ and Li6.5La3Zr1.35Ta0.6M0.05O12 (M = Mg, Ca, Sr, Ba) with the co-substitution of alkaline earth metal ions and Ta5+ for Zr4+ are prepared. The sole substitution of alkaline earth metal elements for Zr in LLZO have little effects on improving ionic conductivity, while the modified LLZO with synergistically co-doping Ta and alkaline earth metal elements can achieve the great enhancement of ionic conductivity. The order of ionic conductivity influenced by Ta5+ and alkaline earth metal ions (Mg2+, Ca2+, Sr2+, Ba2+) co-substitution for Zr4+ demonstrates a strong correlation with ionic radii of Mg2+/Ca2+/Sr2+/Ba2+. Particularly, the enhanced Li6.5La3Zr1.35Ta0.6Mg0.05O12 with the joint substitution of Mg and Ta delivers a highest ionic conductivity of 3.45 × 10−4 S cm−1 at room temperature.