Molecular Bridging of Ceramic–Polymer Interfaces Enables Fast Ion Transport and Long‐Life Solid‐State Lithium Metal Batteries

ABSTRACT Composite solid electrolytes (CSEs) are promising for high‐energy solid‐state lithium metal batteries, yet weakly coupled ceramic/polymer interfaces often induce filler aggregation, interfacial defects, and discontinuous Li + transport. Here, we establish a molecular‐bridging strategy using bifunctional PFDTES to couple LLZTO with a fluorinated polymer framework. PFDTES chemically anchors to hydroxylated LLZTO through hydrolysis–condensation reactions, while its perfluorinated segment enhances affinity toward PVDF‐HFP, thereby transforming weakly contacted ceramic/polymer interfaces into more strongly coupled interphases. This dual‐ended molecular bridging suppresses filler aggregation and interfacial defects while reshaping the local Li + coordination environment. The resulting polar interfacial environment weakens Li + –TFSI − association and strong local Li + –ether oxygen coordination, thereby lowering the kinetic barrier for Li + migration across heterogeneous phases. Consequently, PLF‐CSE achieves an ionic conductivity of 5.05 × 10 −4 S cm −1 at 30°C, a Li + transference number of 0.72, and an electrochemical stability window of 5.12 V. More homogeneous Li + flux, together with a LiF/Li 3 N‐rich interphase, enables stable lithium plating/stripping for over 6000 h, while LFP|PLF‐CSE|Li cells retain 92.9% of their capacity after 1000 cycles at 2 C. This work highlights the critical role of molecular bridging in regulating Li + transport across ceramic/polymer interfaces, offering a rational strategy for designing high‐performance CSEs.