Computational Investigation of a Weakly Coordinating Fluorinated Cosolvent as an SEI Contributor in Mixed-Solvent...

In NaPF₆-based triethyl phosphate-trifluoromethylbenzene-dimethyl carbonate electrolytes, trifluoromethylbenzene acts as a bulk solvent modifier that enhances salt solubility and facilitates sodium-ion transport. Using a combination of theoretical approaches that include classical molecular dynamics, reactive molecular dynamics in a tight-binding nanoreactor framework, and density functional theory with transition-state calculations, we investigated the role of trifluoromethylbenzene at the electrode-electrolyte interface. Despite its limited contribution to Na⁺ solvation, our results suggest that trifluoromethylbenzene can still promote the formation of a fluorine solid-electrolyte interphase through facilitated reductive decomposition at the electrode surface, leading to the release of fluoride ions.