Structure-Tunable Fluorinated Polyester Electrolytes with Enhanced Interfacial Stability for Recyclable Solid-State Lithium Metal Batteries.

Polyesters, with their tunable chemical structures and environmental sustainability, have drawn growing attention as solid polymer electrolytes for next-generation solid-state lithium metal batteries (SSLMBs). Through a comprehensive experimental and theoretical study involving the systematic variation of carbon chain lengths in the flexible (diol) and coordinating (diacid) segments, along with selective fluorination at distinct positions along the polymer backbone, 18 types of polyester are fabricated and demonstrate that fluorination at the coordinating segment significantly enhances ionic conductivity by suppressing crystallinity. In contrast, fluorination at the flexible segment reduces ionic migration barriers by providing more homogeneous coordinating sites, thereby improving the lithium-ion transference number, despite increasing chain rigidity and a reduction in overall ionic conductivity. The optimized fluorinated polyesters exhibit excellent interfacial stability with lithium metal by facilitating the formation of a LiF-rich solid electrolyte interphase, as supported by experimental and theoretical simulation analysis. More importantly, to enhance cost-effectiveness and sustainability, a solvent-based recycling route has been developed, achieving substantial recovery yields and notable environmental benefits. This work provides a versatile molecular design and closed-loop recovery strategy for fluorinated polyester electrolytes, advancing their practical application in high-energy and sustainable SSLMBs.