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

TL;DR

This paper demonstrates that increasing ion size asymmetry in polymer electrolytes enhances ion dispersion and transport by promoting better mixing, challenging the conventional separation paradigm and offering new design strategies for energy storage materials.

Contribution

It reveals that a high ion size ratio improves ion-polymer mixing and transport, providing a novel approach to optimize solid polymer electrolytes for energy storage.

Findings

High ion size ratio promotes better ion dispersion.

Ion-dipole interactions dominate over ion-ion interactions.

Enhanced ion transport observed with size asymmetry.

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.