Sol–Gel‐Derived Lithium Superionic Conductor Li1.5Al0.5Ge1.5(PO4)3 Electrolyte for Solid‐State Lithium–Oxygen Batteries

Lithium aluminium germanium phosphate (LAGP) is attracting a great deal of attention as a solid electrolyte for lithium–oxygen (Li–O2) batteries due to its high ionic conductivity. In this study, LAGP is prepared by a sol–gel process using comparatively low‐cost GeCl2 as one of the reactants. The final product (LAGP) is obtained by sintering the dry precursor gel at 900 °C for 6 h. The influence of the duration of water evaporation during polymerization on the microstructure of LAGP has been examined. The structure, morphology, and electrochemical properties of LAGP are investigated by employing X‐ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption analysis, and electrochemical impedance spectroscopy. XRD studies confirm the formation of Li1.5Al0.5Ge1.5(PO4)3 as a primary phase along with small amounts of AlPO4 and Li2O as impurity phases. LAGP specimens have ionic conductivities in the range of 10−4 to 10−5 S cm−1 at room temperature. In addition, LAGP also exhibits electrocatalytic activity towards the oxygen‐reduction and evolution reactions. These results demonstrate the potential of LAGP prepared by sol–gel processes as a solid electrolyte for lithium‐ion conduction in solid‐state lithium–oxygen batteries.