High Correlation Between Li⁺ Solvation Energy and Li⁺ Ionic Conductivity in Lithium Metal Battery Electrolytes

In lithium metal batteries, accurately estimating the Li⁺ solvation ability of solvents is essential for effectively modulating the Li⁺ solvation sheath to form a stable interphase and achieve high ionic conductivity. However, previous studies have shown that the theoretically calculated Li⁺ binding energy, commonly used to evaluate solvation ability, exhibits only a moderate correlation with experimentally measured ionic conductivity (R² = 0.68). In this study, to determine the effective theoretical descriptor for evaluating the solvation ability, Li⁺ solvation energy was adopted instead of Li⁺ binding energy, and its correlation with ionic conductivity was compared. Using a sophisticated calculation model that considers the Li⁺ counter anion and solvent, it was demonstrated that the tendency between the calculated Li⁺ solvation energies and experimentally measured ionic conductivities is highly consistent (R² = 0.97). Therefore, Li⁺ solvation energy is suggested as the theoretical descriptor for evaluating solvation ability. All these findings encourage the development of effective molecular design of solvents for lithium metal batteries.