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

Effects of alkaline earth metal elements and their synergistic roles with Ta for the modified Li 7 La 3 Zr 2 O 12 (LLZO) are discussed. Li 7.1 La 3 Zr 1.95 M 0.05 O 12 (M = Mg, Ca, Sr, Ba) with the substitution of alkaline earth metal ions for Zr 4+ and Li 6.5 La 3 Zr 1.35 Ta 0.6 M 0.05 O 12 (M = Mg, Ca, Sr, Ba) with the co-substitution of alkaline earth metal ions and Ta 5+ for Zr 4+ 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 Ta 5+ and alkaline earth metal ions (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) co-substitution for Zr 4+ demonstrates a strong correlation with ionic radii of Mg 2+ /Ca 2+ /Sr 2+ /Ba 2+ . Particularly, the enhanced Li 6.5 La 3 Zr 1.35 Ta 0.6 Mg 0.05 O 12 with the joint substitution of Mg and Ta delivers a highest ionic conductivity of 3.45 × 10 −4 S cm −1 at room temperature.