Ferroelectric Low‐Tortuosity Separators for Dendrite‐Free Solid‐State Lithium Metal Batteries

ABSTRACT Lithium metal batteries face uncontrollable dendrite growth and interfacial instability. While solid polymer electrolytes (SPEs) via in situ polymerization offer a promising solution, they require functional separators—yet commercial ones suffer from tortuous pores, poor wettability, and low thermal stability. Here, we engineer ferroelectric BaTiO 3 ‐coated track‐etched membranes (BTEMs) with vertically aligned channels to address these challenges. The low‐tortuosity architecture shortens Li + diffusion pathways, while ferroelectric polarization homogenizes electric field and Li + flux. Coupled with in situ polymerized poly(1,3‐dioxolane) (PDOL) electrolyte, the BTEMs‐based SPE achieves exceptional ionic conductivity (σ = 0.12 mS cm −1 ) and transference number ( = 0.73). The resulting solid‐state batteries deliver >1000 h of stable Li plating/stripping and Li||LiFePO 4 full cells retaining 80.2% capacity after 260 cycles at 0.4 C. The pouch cell delivers a discharge capacity of 5.83 mAh and remains operational even after folding or cutting. Both experimental and computational studies confirm that the low‐tortuosity BTEMs shorten the Li + transport pathway and drive electric field redistribution, thereby achieving uniform Li deposition. Overall, this work establishes a paradigm of geometrically engineered ferroelectric separators that concurrently resolve ionic transport bottlenecks and dendrite propagation, paving the way for next‐generation LMBs with high performance and safety.