Investigating ionic liquid hydration effects at high temperatures: Insights from classic molecular dynamics simulations

Abstract

In this study, we conducted an investigation into the structural and energetic properties of two distinct ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate [Emim][BF4] and choline-glycine [Ch][Gly], varying the hydration level from 10% to 90%. Molecular dynamics simulations were employed to assess the behavior of these ionic liquids when hydrated with water molecules. Our analysis focused on elucidating the effects of hydration on characteristics such as the mobility of ionic pairs. For the [Ch][Gly]–water system, we have conducted an analysis of hydrogen bonds (HBs), highlighting the effects of high-temperature hydration. Furthermore, we explored the changes in the dielectric constant induced by hydration, revealing significant potential for both ionic liquids in energy storage applications. From the Einstein diffusion coefficient, we observed a substantial increase in the mobility of system components with hydration, especially in the [Emim][BF4]-based ionic liquid. We also delved into the Kirkwood G-factor, obtaining insights into dipolar interactions in the ionic liquids, revealing differences between the two systems that could impact electrical properties when these ionic liquids are used as electrolytes in supercapacitors.