Tailoring Lithium‐Ion Transport and Solvation Structure via Fluorination Patterns in Polymer Electrolytes

Abstract Solid polymer electrolytes based on poly(ethylene oxide) (PEO) are promising candidates for next‐generation Li ⁺ batteries but suffer from limited Li ⁺ transference numbers and stability issues at high voltages. Fluorination emerges as an effective chemical modification to improve both ionic transport and electrochemical stability; however, it is difficult to precisely control fluorination patterns experimentally, making simulations essential for evaluating their impact on Li ⁺ transport and guiding fluorination design. In this work, a systematically investigate is conducted on fluorinated PEO‐based electrolytes (F0F1, F0F2, F1F1, F1F2, and F2F2), elucidating two distinct fluorination regimes—low‐fluorination (F0F1, F0F2, F1F1) and high‐fluorination (F1F2, F2F2)—which differ markedly in solvation structures, ion clustering behaviors, and ion dynamics. Polymers in the low‐fluorination regime show strong polymer–Li ⁺ coordination, restricting ion mobility despite effective salt dissociation. In contrast, high‐fluorination regime polymers exhibit rapid polymer segmental dynamics but extensive ion clustering that reduces free‐ion concentration, thus limiting conductivity. Optimal fluorination patterns balance these competing effects, significantly enhancing Li ⁺ transference numbers and overall electrolyte efficacy. These findings provide critical theoretical insights for the rational design of advanced, high‐performance polymer electrolytes.