Ultrahigh‐Temperature‐Tolerance Lithium Metal Batteries Enabled by Molecular‐Level Polymer Configuration Design with Low‐Entropy‐Penalty Effect

Abstract Despite their immense potential for next‐generation energy storage, the practical implementation of temperature‐tolerant lithium metal batteries (LMBs) under extreme thermal conditions continues to face formidable challenges. In this study, an ultrahigh‐temperature‐tolerance polymer‐based electrolyte (UPE) prototype with a low‐entropy‐penalty effect is proposed. This electrolyte features a carefully engineered molecular configuration that enables stable operation of polymer‐based LMBs across a broad temperature range (25–150 °C). Comprehensive experimental and theoretical analyses confirm that the unique “ester‐ether‐fluorinated segment” architecture enables the formation of a robust coordination framework through Li⁺‐multivalent ether/ester interactions and effective Li + ‐ether strong‐solvent‐cage decoupling. The resulting polymer electrolyte integrates reactive carboxyl groups, alkali‐metal‐soluble ether moieties, and fluorinated segments that provide inert yet efficient ion conduction pathways. This synergistic configuration achieves high ionic conductivity, significantly improved lithium‐ion transference numbers, and excellent interfacial compatibility with lithium metal. This work presents a molecular‐level polymer design framework, providing a compelling direction for the development of high‐performance, thermally stable lithium‐metal batteries.