Molecular insights of Na+ ion in binary and ternary imidazolium ionic liquid mixtures

We employ all-atom molecular dynamics simulations to investigate the intermolecular structure, dynamics, and thermodynamic properties of Na+ ions in ionic liquids (ILs) mixture in water. We have considered five different binary and two ternary combinations of IL mixtures having [EMIM]+ as a common cation and four different anions, such as Benzoate [BEZ]−, Nitrate [NO<inf>3</inf>]−, Hexafluorophosphate [PF<inf>6</inf>]−, and Tetrafluoroborate [BF<inf>4</inf>]−. Several structural, dynamic, and thermodynamic properties are examined, which include radial distribution functions (RDF), ion self-diffusion coefficients, ionic conductivity, and solvation free energy. The values of the self-diffusion coefficient for Na+ ions are significantly higher in the [EMIM][BF<inf>4</inf>] and [EMIM][NO<inf>3</inf>] mixtures when compared to other IL mixtures. This further presents that the IL mixture comprising [EMIM][BF<inf>4</inf>] along with [EMIM][NO<inf>3</inf>] has a higher ionic conductivity in the presence of water. The corresponding solvation-free energy of Na+ ions (ΔG<inf>Na</inf>) also aligns with the observed structural transition. Among all the systems, the ternary mixtures show higher ionic conductivity than the binary system. Overall, this manuscript presents a fundamental behavior of IL mixture (binary vs. ternary) solvation behavior and its influence on the Na+ ion in the presence of water. © 2025 Elsevier B.V., All rights reserved.