Dissolution behavior, thermodynamic analysis and molecular simulation of lithium bis(fluorosulfonyl)imide in organic solvent at 273.15 K to 313.15 K

Abstract

The solubility of LiFSI in ethanol, n-propanol, isopropanol, n-butanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate at 273.15 K to 313.15 K were determined. Elevated temperatures can actuate the continued mixing of LIFSI in the 11 fluids outlined above. In comparison, the addition of an alkyl group to the carbon chain of a structurally similar solvent molecule will result in a smaller solubility of LiFSI. Overall the molar solubility of LiFSI in esters are significantly higher than the other four alcohols. Besides, the corresponding theoretical results were mounted by fitting the classical equation. The deviation of the fitted values from the measured values showed that the Apelblat equation and Yaws model was more effectively in fitting the solubility of LiFSI. Then, The Δ_solH^o, Δ_solG^o, Δ_solS^o of electrolyte solution were discussed by Van’t Hoff equation. Their fruits implied that the dissolution of LiFSI is found to be accompanied by heat absorption and entropy gain processes. Finally, the solvent molecular polarity index and solvation free energy were calculated by molecular visualization analysis and molecular dynamics simulation, and the correlation analysis with solubility order was carried out to illustrate the role of molecular features on the LiFSI solubility was explained. Electrostatic interactions and molecular polarity are the leading players in determining its solubility limit. These results will provide valuable reference for the purification of LiFSI and the development of new electrolyte solutions.