Probing Solvent-Ion Interactions using Experiment and Theory
University of Texas at Austin
Electrolytes serve a pivotal role in the function of rechargeable batteries by allowing free metal cations to migrate between the two principle electrodes. This functionality allows for reversible charging and discharging of the cell continuing its use over a longer period of time. Solvation of the metal cation within the chosen electrolyte is a complex process, integral in the ability of the cation to move between electrodes and in the formation of cation consuming byproducts. To better understand the mechanics of this process, we investigate the coordination of lithium ions (Li+) in aprotic solvent Propylene Carbonate (PC). Experiments included the study of an array of different Lithium salts bearing anions of various ionic radii, such as LiBF4, LiPF6, LiClO4, and LiBOB in PC by Raman Spectroscopy. These results were supplemented via Vienna Ab-initio Simulation Package (VASP) calculations to aid in identifying the mechanism of Li+ coordination. Examination of the Raman spectra of Fluorine bearing anions lead to the formation of a hypothesis regarding anharmonic coupling of solvent molecules instigated by Lithium's presence. The primary purpose of these studies is to elucidate the mechanistic changes of Li+ solvation as the accompanying anionic group is varied.