Investigation on lithium ion conductivity and structural stability of yttrium-substituted Li7La3Zr2O12

Advanced Li-air battery architecture demands a high Li+ conductive solid electrolyte membrane that is electrochemically stable against metallic lithium and aqueous electrolyte. In this work, an investigation has been carried out on the microstructure, Li+ conduction behaviour and structural stability of Li7La3-x Y x Zr2O12 (x = 0.125, 0.25 and 0.50) prepared by conventional solid-state reaction technique. The phase analysis of Li7La3-x Y x Zr2O12 (x = 0.125, 0.25 and 0.50) sintered at 1200 °C by powder X-ray diffraction (PXRD) and Raman confirms the formation of high Li+ conductive cubic phase ( $$ Ia\overline{3}d $$ ) lithium garnets. Among the investigated lithium garnets, Li7La2.75Y0.25Zr2O12 sintered at 1200 °C exhibits a maximized room temperature total (bulk + grain boundary) Li+ conductivity of 3.21 × 10−4 S cm−1 along with improved relative density of 96 %. The preliminary investigation on the structural stability of Li7La2.75Y0.25Zr2O12 in the solutions of 1 M LiCl, dist. H2O and 1 M LiOH at 30 °C/50 °C indicates that the Li7La2.75Y0.25Zr2O12 is relatively stable against 1 M LiCl and dist. H2O. Further electrochemical investigation is essential for practical application of Li7La2.75Y0.25Zr2O12 as protective solid electrolyte membrane in aqueous Li-air battery.