Local Acidity as a Corrosiveness Descriptor of Fluorinated Ether Solvents in Lithium–Metal Batteries

ABSTRACT Electrolyte engineering based on solvent fluorination has proven effective for stabilizing lithium (Li) metal batteries by weakening the Li + ‐solvent interaction. However, the influence of fluorination on the chemical reactivity of an electrolyte toward Li metal remains poorly understood. Here, the effects of fluorination are systematically investigated by increasing the degree of fluorination (from 2 to 5 substituents) of the terminal alkyl moieties of the 1‐ethoxy‐2‐methoxyethane (EME) and 1‐(2‐methoxyethoxy)propane (MEP) backbones (denoted F2EME, F4MEP, and F5MEP). Fluorination‐induced corrosion deviates from that suggested by conventionally calculated lowest unoccupied molecular orbital (LUMO)‐based rationales; instead, it is quantitatively described by the local pK a as a site‐specific thermodynamic descriptor of the fluorination‐induced electronic effect. Among the three …