Fluorinated Segments Engineering with Strongly Electron Withdrawing Effect in Quasi Solid State Electrolyte for Fast Charging and High Voltage Lithium Metal Batteries

Abstract Polyether electrolytes (PE) suffer from strong Li+–ether oxygen coordination and poor high voltage oxidative stability. Herein, we use in situ copolymerization to covalently graft the strongly electron-withdrawing −CF3 groups onto the backbone, synthesizing FPME, which delocalizes electron density around ether oxygens. Unlike physical blending, this covalent approach ensures molecular uniformity of electron-withdrawing effects, creating a weak coordination microenvironment that reshapes Li+ solvation and expedites ion transport. The electrolyte achieves 1.30 mS cm–1 at 30 °C. The −CF3 groups prevent lone-pair electron loss from ether oxygens, suppressing cathode side reactions and enhancing oxidation resistance, with an electrochemical window of 5.63 V, which contributes to enhanced long-term cycling stability. LFP||Li cell retains 65% capacity after 1000 cycles at 10 C, while NCM811||Li cell achieves 71% after 500 cycles at 1 C. This strategy enables fast charging and high energy density for solid-state lithium-metal batteries.