Ferroelectrically Modulated Composite Polymer Electrolyte Enabling Accelerated Ion Transport and Stable Interfaces for Solid‐State Lithium Metal Batteries

ABSTRACT Polymer‐based solid‐state electrolytes are attractive for solid‐state lithium (Li) metal batteries owing to their flexibility, lightweight nature, and scalable manufacturability. However, their practical application remains constrained by sluggish Li ⁺ transport, severe anion migration, and unstable electrode‐electrolyte interfaces. Herein, we reported a ferroelectrically modulated composite polymer solid‐state electrolyte, constructed by integrating an electrospun fibrous framework containing ferroelectric K _0.5 Na _0.5 NbO ₃ into a solid polymer electrolyte matrix. The incorporation of ferroelectric fillers effectively suppresses polymer crystallinity, promotes the transformation of a polar β‐phase of poly(vinylidene fluoride‐co‐hexafluoropropylene), and immobilizes TFSI ⁻ anions through strong surface interactions, thereby reconstructing the local solvation environment and significantly enhancing Li ⁺ transport kinetics. Meanwhile, spatially distributed ferroelectric domains regulate local electric‐field distribution and alleviate space‐charge accumulation, enabling interconnected Li ⁺ transport pathways with homogenized ionic flux and reduced interfacial polarization, which collectively suppress Li dendrite growth. The obtained solid‐state electrolytes deliver a high ionic conductivity of 6.7×10 ⁻⁴ S cm ⁻¹ with a Li ⁺ transference number of 0.68 at 30°C, and corresponding solid‐state batteries demonstrate stably cycling over 300 cycles at 1.0 C. The resulting pouch cells exhibit excellent electrochemical stability and safety performance, underscoring a ferroelectric‐enabled strategy for simultaneously addressing ion‐transport and interfacial challenges in advanced polymer‐based solid‐state electrolytes.