Design of Novel Solid-State Electrolytes Based on Plastic Crystals of Quinuclidinolium Methanesulfonate for Proton Conduction

A series of methanesulfonate salts with various globular cations, including the achiral 3-quinuclidonium [QHco]+ , the racemic (3)-hydroxyquinuclidinium [QHrac]+ , and the enantiopure (3)-hydroxyquinuclidinium R-[QH]+ , have been synthesized and structurally characterized. Despite the high degree of similarity among components, only the enantiopure salt R- [QH]MS was found to undergo a reversible plastic transition at high temperature. Electrochemical impedance spectroscopy was successfully applied to study proton conductivity associated with temperature variations and the plastic phase transition under inert and dry conditions. Ionic conductivity at RT was lower than 10−11 S cm−1 and drastically increased up to 1.03 × 10−3 S cm−1 at 145 °C due to the onset of the plastic phase transition.