Fig. 4: Theoretical and experimental studies on the Li⁺ solvation structures and electrolyte configurations.

a Fitted Raman curves of anions for different anion pairs of free anions, SSIP (solvent-separated ion pairs), and CIP (contact ion pairs), and their ratio comparison, with enlargement in the range of 710–745 cm⁻¹ for the LiFSI electrolyte in the inset. The peaks located at 667 and 697 cm⁻¹ can be assigned to the C-S symmetric and asymmetric stretching vibrations of free DMSO, respectively. The peaks at 676 and 708 cm⁻¹ are attributed to the C-S symmetric and asymmetric stretching vibrations of DMSO molecules that solvate with Li⁺ ions^17,39,55,56. b Left Y-axis: coordination numbers of different anions (yellow) and DMSO solvent (yellow slashes) in inner solvation shells by MD; right Y-axis: Binding free energy ΔG_bind between Li⁺ and different anions calculated by DFT. MD simulation boxes, representative structures of Li⁺ solvation clusters, and the electrolyte configurations based on the percentages of different Li⁺ solvation clusters for c LiNO₃, d LiBF₄, e LiFSI, and f LiTFSI electrolytes. Colour scheme of molecules: Li, pink; C, light blue; H, white; O, red; N, navy; S, yellow; F, purple; and B, blue.