Electrochemical properties of Li8 − 2xMxZrO6 (M = Mg, Sr) solid electrolytes

•The transport properties of the Li8 − 2xMxZrO6 (M = Mg, Sr) system were studied.•The mechanism of Li+ ion transfer in the Li8 − 2xMxZrO6 (M = Mg, Sr) was proposed.•The stability with respect to lithium of Li8 − 2xMxZrO6 (M = Mg, Sr) was determined.•Novel solid electrolyte with conductivity 4 · 10− 3 S/cm at 250 °C was obtained.

This study deals with the effect of alkaline-earth metal substitution on the transport properties of the solid electrolytes Li8 − 2xMxZrO6 (M = Mg, Sr). The region of the solid solution in the Li8 − 2xMxZrO6 (M = Mg, Sr) systems was determined. The best effect of the dopant on the conductivity was observed for solid electrolyte Li7.85Mg0.075ZrO6: the grain boundary conductivity for Li7.85Mg0.075ZrO6 is 2.3 · 10− 3, for Li8ZrO6 is 1.7 · 10− 4 S/cm; the bulk conductivity for Li7.85Mg0.075ZrO6 is 7.2 · 10− 3, and for Li8ZrO6 is 1.5 · 10− 4 S/cm at 355 °C. From the nuclear magnetic resonance (NMR) and impedance spectroscopy studies we propose the mechanism of Li+ ion transfer in the phase Li8ZrO6 and the solid solutions based on it. The ceramic samples of Li8 − 2xMxZrO6 (M = Mg, Sr) solid solutions were found to be stable with respect to lithium.