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The key hurdle to the practical application of polymeric electrolytes in high‐energy‐density solid lithium‐metal batteries is the sluggish Li+ mobility and inferior electrode/electrolyte interfacial stability. Herein, a dynamic supramolecular polymer electrolyte (SH‐SPE) with loosely coordinating structure is synthesized based on poly(hexafluoroisopropyl methacrylate‐co‐N‐methylmethacrylamide) (PHFNMA) and single‐ion lithiated polyvinyl formal. The weak anti‐cooperative H‐bonds between the two polymers endow SH‐SPE with a self‐healing ability and improved toughness. Meanwhile, the good flexibility and widened energy gap of PHFNMA enable SH‐SPE with efficient ion transport and superior interfacial stability in high‐voltage battery systems. As a result, the as‐prepared SH‐SPE exhibits an ionic conductivity of 2.30 × 10−4 S cm−1, lithium‐ion transference number of 0.74, electrochemical stability window beyond 4.8 V, and tensile strength up to 11.9 MPa as well as excellent adaptability with volume change of the electrodes. In addition, no major electrolyte decomposition inside batteries made from SH‐SPE and LiNi0.8Mn0.1Co0.1O2 cathode can be observed in the in situ differential electrochemical mass spectrometry test. This study provides a new methodology for the macromolecular design of polymer electrolytes to address the interfacial issues in high‐voltage solid batteries.

Poly(1,3-dioxolane) (PDOL)-based solid electrolytes are expected to be exploited in solid-state lithium metal batteries (SLMBs) due to their high ionic conductivity, good lithium metal compatibility, and facile preparation method of in-situ polymerization in cells. However, inferior structural stability and low Li-ion transference number (tLi+) still impede PDOL from authentic commercialization. Herein we propose a novel ultrathin crosslinked PDOL-based electrolyte (PTADOL), which is prepared via a multifunctional trimethylolpropane tris[3-(2-methyl-1-aziridine) propionate] additive. The in-situ formed PTADOL not only affords an integrated network configuration with stabilized electrode/electrolyte interface, but also achieves improved oxidative stability, excellent thermal stability, and superior flame retardancy. Moreover, PTADOL has rational O-Li+ coordination for fast Li+ transport, which enhances both ionic conductivity and tLi+. Based on the ultra-stable PTADOL, the high voltage LiNi0.8Mn0.1Co0.1O2||Li batteries exhibit excellent electrochemical performance without electrolyte degradation. This work provides a practical approach to designing a highly stable solid polymer electrolyte for high-performance SLMBs.