Impact of Electron-Withdrawing Groups on Ion Transport and Structure in Lithium Borate Ionic Liquids

TL;DR

This study uses molecular dynamics simulations to explore how electron-withdrawing groups influence ion transport and structure in lithium borate ionic liquids, revealing mechanisms that could inform better electrolyte design.

Contribution

It provides new insights into the role of electron-withdrawing groups in regulating lithium ion transport mechanisms in lithium ionic liquids.

Findings

Correlated ion dynamics govern transport in LILs.

Electron-withdrawing groups regulate Li transport mechanisms.

Higher fluorine saturation increases inhomogeneity in properties.

Abstract

Among the distinctive structural features of lithium ionic liquids (LILs), a novel class of single-component electrolytes, the variation of the electron-withdrawing group stands out as a key factor in determining their dynamics. To understand this phenomenon, we conducted molecular dynamics (MD) simulations for LILs based on hexafluoro-2-propanoxy (LIL2), hexafluoro-2-methyl-2-propanoxy (LIL4), and trifluoro-2-propanoxy (LIL6) derivatives. Results revealed that correlated ion dynamics govern the general transport characteristics in LILs, while the electron-withdrawing group regulates the Li transport mechanism. Upon saturation by fluorine atoms, LILs exhibit higher inhomogeneity in their transport and structure properties. Strong coordination along the ethoxide group promotes jumps of Li across positive domains, while in fluorine-poor LILs, stronger coordination in proximity to boron atoms carries the anion along Li transport. Understanding the results of MD simulation will aid the further design and widespread use of this class of electrolytes in production of the energy storage and conversion devices