Understanding\nIon Transport in Alkyl Dicarbonates:\nAn Experimental and Computational Study

In an effort to improve safety and cycling stability\nof liquid\nelectrolytes, the use of dicarbonates has been explored. In this study,\nfour dicarbonate structures with varying end groups and spacers are\ninvestigated. The effect of these structural differences on the physical\nand ion transport properties is elucidated, showing that the end group\nhas a significant influence on ion transport. The solvation structure\nand ion transport in the dicarbonates are compared to those of the\nlinear carbonates dimethyl carbonate (DMC) and diethyl carbonate (DEC).\nAlthough the carbonate coordination numbers (CN) are similar in the\ndifferent systems, the CN from the anion is higher in dicarbonate\nelectrolytes. At low salt concentrations, rapid solvent exchange is\nobserved in the DMC- and DEC-containing systems, transitioning to\na more correlated ion transport at high salt concentration. In contrast,\nthe exchange of solvents around lithium ions (Li<sup>+</sup>) is limited\nin the dicarbonate systems regardless of the salt concentration, with\nonly one carbonate group from each molecule participating in the coordination.\nIn addition, according to the molecular dynamics simulations, Li<sup>+</sup> mainly moves together with coordinating dicarbonate molecules\nand anion(s).