Elucidating Kinetic‐Mediated Polymerization Behavior for In Situ Formation of Fluorine‐Containing Gel Polymer Electrolyte

ABSTRACT Fluorinated gel polymer electrolytes (FGPEs) prepared via in situ polymerization are expected to expedite the large‐scale application of lithium metal batteries (LMBs) by enabling stable LiF‐rich solid electrolyte interphases (SEIs) and good compatibility with high‐voltage cathodes. However, the electron‐withdrawing nature of fluorine units retards polymerization kinetics of such monomers, resulting in GPEs with compromised mechanical performance and cycling durability. Herein, a design principle for in situ formation of fluorinated copolymers is proposed to regulate the polymerization kinetics of trifluoroethyl methacrylate (TFEMA)‐typed monomers. Such strategy yields relatively uniform polymer chains with moderate molecular weights, which are subsequently crosslinked to form a robust fluorinated–nitrogenated copolymer network (FNPE). The tailored polymer matrix integrates the capabilities to form a LiF‐containing SEI promoted by fluorinated segments, enhanced mechanical robustness, and a Li 3 N‐rich interphase contributed by the N ‐isopropylacrylamide (NIPAM) domains. Consequently, the FNPE achieves NCM811(6.8 mg cm −2 , 1.2 mAh cm −2 )//Li full cells with high capacity retention (> 80%, 225 cycles), and applicable in wide temperature range (−15 to 60°C) and pouch cell configuration (40 µm Li). Through experimental and multiscale modeling investigations, this work elucidates the intrinsic kinetic challenge for in situ formed FGPEs and provides a new design principle of copolymer‐type electrolytes for durable LMBs.