Fluorinated ether-anchored solid polymer electrolyte for lithium metal batteries for low-temperature adaptability

Abstract

Solid polymer electrolytes (SPEs) are promising for safe and scalable all-solid-state lithium batteries, but lowtemperature ionic transport and interfacial instability limit their practical use. Here, we present a fluorinatedether (FE)-anchored polymer electrolyte (FAPE) based on a PEGDME semi-interpenetrating network, designed to overcome these challenges. FE units anchor onto ether chains via C- H & sdot;& sdot;& sdot;O interaction, suppressing crystallization, weakening Li*-EO coordination, and promoting formation of inorganic-rich, anion-derived interphases. FAPE exhibits high ionic conductivity down to -20 degrees C, intrinsic nonflammability, and an expanded electrochemical stability window. Lithium metal cells with FAPE demonstrate enhanced Coulombic efficiency, extended cycling stability, and higher critical current densities compared to conventional PEGDME-based SPEs. Full cells and prototype pouch cells retain high capacities under both ambient and sub-zero temperatures, highlighting their practical applicability. This molecular anchoring strategy provides a versatile platform to tailor solvation structure and interphase chemistry, enabling wide-temperature, safe, and durable operation in high-energy solidstate lithium metal batteries.