Synergic effect of CaI and LiI on ionic conductivity of solution-based synthesized LiPS solid electrolyte.

LiPS doped with CaX (X = Cl, Br, I) and LiI solid electrolytes were successfully prepared by liquid-phase synthesis using acetonitrile as the reaction medium. Their structure was investigated using XRD, Raman spectroscopy and SEM-EDS. The data obtained from complex impedance spectroscopy was analyzed to study the ionic conductivity and relaxation dynamics in the prepared samples. The XRD results suggested that a part of CaX and LiI incorporated into the structure of LiPS, while the remaining part existed at the grain boundary of the LiPS particle. The Raman peak positions of PS and PS ions in samples 90LiPS-5CaI and 90LiPS-5CaI-5LiI had shifted as compared to the LiPS sample, showing that CaI addition affected the vibration of PS and PS ions. EDS results indicated that CaI and LiI were well dispersed in the prepared powder sample. The ionic conductivity at 25 °C of sample 90LiPS-5CaI-5LiI reached a very high value of 3.1 mS cm due to the improvement of Li-ion movement at the grain boundary and structural improvement upon CaI and LiI doping. This study encouraged the application of LiPS in all-solid-state Li-ion batteries.