Ionic Conduction and Electric Modulus in Li<sub>2</sub>S–CaS and Ca<i>X</i><sub>2</sub> (<i>X</i> = F, Cl, Br, and I) Nanocomposites

Technology for ion conduction in Li2S nanostructure has attracted considerable interest for achieving the intrinsic performance of Li-S batteries and for obtaining highly conductive materials. Herein, a quantitative relationship between ion transport and relaxation behavior in the Li2S–CaS nanocomposite is revealed based on complex conductivity and electric modulus formalism. Li2S–CaS nanocomposites prepared by high-energy ball milling show higher conductivity and activation energy for conduction than pure Li2S. The activation energy for relaxation is lower than the activation energy for conduction in 80Li2S·20CaS (mol%). The long-range ion transport involves high activation energy compared with the hopping of carriers at localized states in 80Li2S·20CaS. Additionally, the dual doping of Ca and halogen reduces the activation energy for conduction and improves the conductivity of Li2S. The findings show important insight for understanding ion transport in nanocomposites containing a Li2S nanostructure.