Breaking Ion Clusters: Size Asymmetry for Faster Ion Transport in Polymer Electrolytes

Abstract

Solid polymer electrolytes (SPEs) are ion-containing solid materials composed of a polymer matrix that enables ionic transport while maintaining the mechanical stability. The conventional wisdom is that for a high ion concentration, ions microphase separate from the polymer matrix, resulting in poor conductivity. Instead, we show that a high ion size ratio promotes better mixing of the ions with the polymer matrix. Under these conditions, the ion-dipole moment interaction dominates over the ion-ion interaction and improves the ion dispersion in the polymer matrix. The ion size ratio is thus a key to tailor the properties of these materials with immediate relevance to the development of SPEs for energy storage devices.