LIC was synthesized based on a convenient two-step procedure, comprising mechanochemical mixing via high-energy ball milling and subsequent annealing step. The corresponding XRD patterns for LIC before and after annealing are shown in Fig. . Both patterns can be indexed with monoclinic rock-salt structure (space group: C2/m). No phases other than LIC can be observed. The surface morphology as shown in SEM image in Fig. reveals the formation of elongated particles of LIC. After annealing LIC shows narrow reflections indicating an increased crystallinity, around 82.5 %. To determine the Li-ion conductivity of LIC, EIS measurements in a temperature range between 25 °C to 65 °C were performed. The corresponding Nyquist plots are shown in Figure , revealing one electrical relaxation process: an onset of a high-frequency semicircle and a spike toward low frequencies. Due to the low amount of high-frequency data points, the resistive part of the arc has been simply fitted by a resistance element, which can be attributed to the total Li-ion conduction of the pellet. The low-frequency spike is typically related to the electrodes. Adding another R|CPE element improves the fit due to the nonideality of the blocking electrode but has no physical meaning. The total Li-ion conductivity of LIC at room temperature was calculated to be 1.44 mS/cm, which is similar to the values reported in the literature and one to two orders in magnitude higher than that of other promising solid electrolyte-based traditional coating candidates, such as garnet-type LLZO , NASICON-type LAGP , etc. In Fig. the temperature dependence of the Li-ion conductivity is shown. It follows Arrhenius behavior according to σT = σ0 exp(-Ea/(kBT)), where σ0 represents the pre-exponential factor. The activation energy Ea is 0.31 eV, which is similar to values reported previously .