From Clustered Motion to Percolation: Unveiling Correlated Lithium Ion Dynamics in Ionic Liquid Mixtures via an Ab Initio Force Field

Understanding the local solvation structure and correlated ion motion in lithium salt/ionic liquid mixtures is critical for designing high-performance electrolytes. Accurately modeling the complex electrostatic environment of these concentrated systems requires explicit treatment of electronic polarization─an effect often inadequately represented by conventional nonpolarizable force fields. Here, we present a first-principles polarizable force field for lithium ions in ionic liquid environments, derived from ab initio Symmetry-Adapted Perturbation Theory (SAPT) calculations. Particular emphasis is placed on the rigorous determination of atomic polarizabilities, especially in systems with small, high-charge-density species such as Li +, where standard force fields tend to overestimate short-range induction. The resulting force field accurately predicts lithium diffusion coefficients and i…