Influence of solvation on the structural and capacitive properties of electrical double layer capacitors

TL;DR

This study uses molecular dynamics simulations to examine how a non-ionic solvent affects the structure and capacitance of supercapacitors with ionic liquid electrolytes and carbon electrodes, revealing solvent-induced similarities in interfacial properties.

Contribution

It demonstrates how solvation with acetonitrile alters interfacial characteristics of different ionic liquids, providing new insights into electrolyte-electrode interactions.

Findings

Interfacial properties become similar for different ionic liquids when mixed with acetonitrile.

Solvation influences electrode polarization and electrolyte structure at the interface.

The study offers detailed molecular insights into electrolyte behavior in supercapacitors.

Abstract

We use molecular dynamics simulations to explore the impact of a non-ionic solvent on the structural and capacitive properties of supercapacitors based on an ionic liquid electrolyte and carbon electrodes. The study is focused on two pure ionic liquids, namely 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium tetrafluoroborate, and their 1.5 M solutions in acetonitrile. The electrolytes, represented by coarse-grained models, are enclosed between graphite electrodes. We employ a constant potential methodology which allows us to gain insight into the influence of solvation on the polarization of the electrodes as well as the structural and capacitive properties of the electrolytes at the interface. We show that the interfacial characteristics, different for two distinct pure ionic liquids, become very similar upon mixing with acetonitrile.