Enhancing Dicationic IL Performance through Aqueous Binary Mixtures of Mono- and Dicationic ILs: Insights from MD Simulations and DFT Calculations.

In the present study, we investigated the solvation behavior of a binary DIL-MIL mixture across varying water mole fractions using a multiscale approach combining MD simulations with DFT and AIM analyses. This strategy provided molecular-level insights into intermolecular interactions and clarified how hydration modulates both the microscopic structure and macroscopic properties, ultimately improving the performance of the studied DIL. Structural analysis showed that while the primary ion arrangement remains largely stable, hydration significantly reshapes local organization. At low water content, cation clustering, strong ion correlations, and small water domains dominate, with cations preferentially bonding to anions. Higher hydration disrupts these domains, weakens ion-water interactions, strengthens water-water and cation-anion hydrogen bonding, and yields a more homogeneous, bulk-like structure. Hydration markedly enhances ion mobility by weakening ion cages, reducing ion-ion correlations, and accelerating translational and rotational dynamics. DFT analysis further revealed that hydration decreases direct cation-anion binding energies while reinforcing overall stabilization through stronger hydrogen-bonding networks, consistent with increased electron density at bond critical points. These findings provide molecular-level insights into how water incorporation can be used to tune the structural and dynamical properties of DIL-based systems for electrolyte, solvent, catalytic, and other electrochemical applications.