Effect of Ion Mass on Dynamic Correlations in Ionic Liquids
Md. Dipu Ahmed, Zhenghao Zhu, A. A. Khamzin, Stephen J. Paddison, Alexei P. Sokolov, И. И. Попов
Abstract
Ionic liquids (ILs) are a class of liquid salts with distinct properties such as high ionic conductivity, low volatility, and a broad electrochemical window, making them appealing for use in energy storage applications. The ion–ion correlations are some of the key factors that play a critical role in the ionic conductivity of ILs. In this work, we present the study of the impact of ion mass on ion–ion correlations in ILs, applying a combination of broadband dielectric spectroscopy measurements and molecular dynamics simulations. We examined three ILs with the same cation but different anions to consider three different cases of cation–anion masses: M + > M –, M + ≈ M –, and M + < M – . We applied the momentum conservation approach to estimate the contribution of distinct ion–ion correlations from experimental data and obtained good agreement with direct calculations of distinct ion–ion correlations from molecular dynamics simulations. Our findings reveal that relative ion mass has a strong effect on the distinct ion–ion correlations, leading to swapping of the relative amplitude of distinct cation–cation and anion–anion correlations.