Doped superior garnet electrolyte toward all-solid-state Li metal batteries

Li₇La₃Zr₂O₁₂ (LLZO) garnets are one of the most promising solid electrolytes for next generation all-solid-state Li metal batteries due to their high ionic conductivities, chemical stabilities to metallic lithium and wide electrochemical window. Single and co-doped LLZO with Ga, Al, Nb were prepared by solid state reaction and sintered under oxygen atmosphere. Lithium ion conduction properties were investigated through electrochemical impedance spectroscopy in the temperature range of −25 °C–45 °C. Among the doped compositions, Ga doped single phase cubic LLZO shows the highest ionic conductivity of 1.49 × 10⁻³ S/cm at room temperature and activation energy of 0.27eV, which is one of the best results reported in literature so far in terms of doped garnet structured LLZO. All single or co-doped LLZO samples exhibit low electronic conduction which are 4–5 orders of magnitude lower than their corresponding ionic conductivities. Ga-doped garnet LLZO of high ionic conductivity and negligible electronic conduction makes it a superior solid electrolyte for all-solid-state Li metal batteries.