Plastic Crystal Electrolyte Materials: New Perspectives on Solid State Ionics

Abstract

Plastic crystal materials have long been known but have only relatively recently become of interest as solid–state ion conductors. Their properties are often associated with dynamic orientational disorder or rotator motions in the crystalline lattice. This paper describes recent work in the field including the range of organic ionic compounds that exhibit ion conduction at room temperature. Conductivity in some cases is high enough to render the compounds of interest as electrolyte materials in all solid state electrochemical devices. Doping of the plastic crystal phase with a small ion such as Li+ in some cases produces an even higher conductivity. In this case the plastic crystal acts as a solid state “solvent” for the doped ion and supports the conductive motion of the dopant via motions of the matrix ions. These doped materials are also described in detail.