Abstract Solid polymer electrolytes (SPEs) offer an appealing alternative to volatile and flammable organic liquid electrolytes for high‐energy lithium metal batteries (LMBs). Despite their potential, two key challenges, insufficient ionic conductivity and inadequate interfacial performance, continue to hinder practical development. Here, the promising potential of a single‐ion conducting gel polymer electrolyte (SIGPE) derived from a polymerizable deep eutectic monomer (PDEM) is demonstrated. This structure forms dynamic nanophases with a high‐dielectric‐constant dielectricizer through Li + ‐bridged molecular self‐association within a flexible polymer matrix. This design regulates ion pathways to enable rapid Li + conduction, effectively preventing interfacial polarization and promoting ion dissociation, while also exhibiting viscoelastic properties that strengthen interface stability. The resultant SIGPE exhibits a high oxidation voltage of 5.0 V and a near‐unity transference number of 0.86. In the LFP|SIGPE|Li full cell, the formation of an inorganic‐rich SEI layer, driven by hetero species (Li 2 O/LiF), enables a high discharge capacity of 131.9 mAh g −1 at 1 C and stable cycling performance, with 71.9% capacity retention and 99.5% coulombic efficiency after 400 cycles at 1 C and 30 °C. These findings underscore the potential of PDEM‐based SIGPE to enhance performance, safety, and sustainability in LMBs, paving the way for practical use in high‐energy storage systems.

Abstract Solid‐state electrolytes (SSEs) hold significant potential for advancing lithium metal batteries (LMBs) by enhancing safety through the replacement of liquid electrolytes. However, challenges such as low ionic conductivity, limited electrochemical stability, and poor electrolyte/electrode interface compatibility hinder the development of high‐energy‐density LMBs. Herein, a strategy for designing SSEs is proposed using multiple‐bridge engineered composite elastomer electrolytes (CEEs) that incorporate ion‐rotating dipole interactions, ion‐anchoring dipole interactions, and hydrogen bonding, along with a CEE‐based composite elastomer cathode (CEC). This design combines a volume‐adaptive elastomer matrix, a high‐Li + conducting deep eutectic electrolyte, and robust nanowires. The resultant CEE exhibits high ionic conductivity (1.7 × 10 −3 S cm −1 ), a lithium transference number of 0.72, and a wide electrochemical stability window (up to 4.9 V) at 298 K. The engineered uniform Li + flux also promotes stable Li plating/stripping for over 900 h at 0.1 mA cm −2 . Furthermore, the LFP‐based CEC|CEE|Li full cells deliver a reversible capacity of 133 mAh g −1 with 95% retention after 300 cycles in coin cells, and 129 mAh g −1 with 96% retention after 250 cycles in pouch cells at 1 C. This strategy presents a promising approach for designing solid‐state polymer electrolytes to extend the lifespan of high‐energy‐density LMBs.