A Fluoroether Co‐Solvent Engineering Interfacial and Solvation Dynamics for Durable Lithium–Oxygen Batteries

ABSTRACT Lithium–oxygen batteries (LOBs) represent a promising next‐generation energy storage technology due to their ultrahigh theoretical energy density. However, their practical application is hindered by critical challenges including electrolyte volatility and decomposition, lithium anode degradation, and the incomplete reversibility of Li 2 O 2 discharge products. Herein, we design a novel fluorinated ether co‐solvent, 1,1′‐[oxybis[(1,1,2,2‐tetrafluoro‐2,1‐ethanediyl)‐oxy(2,2‐difluoro‐2,1‐etha‐nediyl)]]bis(1,1,1‐trifluoromethanesulfonate) (FTE), which features a high boiling point that effectively suppresses electrolyte evaporation. More importantly, its incorporation promotes the formation of a fluorine‐rich solid electrolyte interphase (SEI) on the lithium metal anode, significantly enhancing interfacial stability. Simultaneously, FTE modulates the Li + solvation structure, steering the growth of Li 2 O 2 away from the conventional toroidal morphology toward a highly decomposable three‐dimensional porous network. These synergistic effects collectively contribute to a substantial improved cycling performance, enabling LOBs with FTE‐modified tetraethylene glycol dimethyl ether based (FTE/TEG‐based) electrolyte to deliver high discharge specific capacities, excellent rate capabilities, and remarkable cycling stability. This study highlights a multifunctional electrolyte design strategy that prioritizes long‐term reversibility, paving the way for practical high‐energy‐density LOBs.