Correlating structure and transport behavior in Li+ and O2 containing pyrrolidinium ionic liquids

Abstract

Ionic liquids are a unique class of materials with several potential applications in electrochemical energy storage. When used in electrolytes, these highly coordinating solvents can influence device performance through their high viscosities and strong solvation behaviors. In this work, we explore the effects of pyrrolidinium cation structure and Li⁺ concentration on transport processes in ionic liquid electrolytes. We present correlated experimental measurements and molecular simulations of Li⁺ mobility and O₂ diffusivity, and connect these results to dynamic molecular structural information and device performance. In the context of Li–O₂/Li–air battery chemistries, we find that Li⁺ mobility is largely influenced by Li⁺-anion coordination, but that both Li⁺ and O₂ diffusion may be affected by variations of the pyrrolidinium cation and Li⁺ concentration.