Solution‐Processable Fluorinated Polymers of Intrinsic Microporosity Enable Ion Transport and Mechanical Shielding for Robust Li Metal Anodes

Suppressing lithium dendrites and stabilizing Li interfaces remain key obstacles for high energy density batteries. Fluorinated regulators show a delicate fluorine‐content dependence, moderate fluorination promotes Li + desolvation and interfacial stability, whereas excessive levels hinder ion transport via resistive LiF formation. To clarify this fluorine‐governed chemistry, a dual‐functional fluorinated PIM was designed as solution‐processable artificial SEI that synergistically regulates ion flux and reinforces interfacial mechanics. The abundant ─CF 3 groups in PX‐HFP impart strong electronegativity and a high modulus (8.37 GPa), establishing an electrostatic barrier that repels anions, elevates the Li + transference number (0.90), and homogenizes Li + flux via surface electric‐field enhancement. Surface spectroscopy further reveals that fluorine modulation favors Li 3 N formation while suppressing excessive LiF accumulation, thereby optimizing ionic transport and interfacial stability. Benefiting from these synergistic effects, PX‐HFP@Li symmetric cells deliver an ultralow overpotential of 44 mV at 40 mA cm − 2 for over 5000 h, Li|Cu cells maintain 250 stable cycles with a Coulombic efficiency of 97.85%, and LFP full cells retain 84.56% capacity after 1300 cycles. These results unveil a mechanical confinement–electric field co‐regulation mechanism enabled by the fluorinated PIM shield, offering a scalable strategy toward robust and safe lithium metal batteries.