The ionic conductivity of the solid-state electrolytes (SEs) was measured via electrochemical impedance spectroscopy (EIS). The SEs were first pelletized by weighing approximately 100 mg of SE, then pressed to ~360 MPa between two Ti rods. The Ti rods also served as blocking electrodes. In the case of LAGP, it was first pelletized to ~360 MPa, then sintered at 700°C for 12 hours in air since LAGP is air stable . Then, to ensure good electrical contact, the sintered LAGP pellet coated with 100 nm Au on both sides via thermal evaporation using a Kurt J. Lesker Nano36 thermal evaporator. The EIS measurements were recorded in the frequency range from 1 MHz to 100 mHz with a 10 mV ac amplitude using a Bio-Logic VMP3 impedance analyzer.