Quantitative Solvation Scale for Lithium Battery Electrolytes

Understanding electrolyte solvation is vital for developing advanced lithium batteries, as solvation structures dictate interfacial chemistry and performance. This study evaluates the reliability of conventional 1D NMR techniques (1H, 7Li, 19F, and 13C) for probing lithium solvation. We demonstrate that absolute chemical shifts often correlate poorly with solvating ability, leading to misleading interpretations-a finding cross-validated by FTIR and DOSY. We identify that the change in chemical shift (Δδ) from 13C NMR serves as a robust descriptor, provided that the probe solvent's solvating ability matches the system. To overcome single-probe limitations, we introduce a multiprobe strategy using ethyl methyl carbonate (EMC), trifluoroethyl methyl carbonate (FEMC), and propylene carbonate (PC). This approach establishes a quantitative solvation scale across weak, intermediate, and strong solvating regimes. The resulting scale shows strong linear correlations with coordination ratios and solvating power, enabling precise linear free-energy relationships. We demonstrate the practical utility of this framework by accurately predicting lithium nitrate solubility and guiding electrolyte design. Ultimately, this work provides a reliable, broadly applicable methodology for advancing next-generation battery electrolytes. Most importantly, this work provides a lithium solvating strength series, offering a highly useful tool for researchers to compare common solvents.