Supramolecular Polymer Ion Conductor with Weakened Li Ion Solvation Enables Room Temperature All‐Solid‐State Lithium Metal Batteries

Abstract Improved durability, enhanced interfacial stability, and room temperature applicability are desirable properties for all‐solid‐state lithium metal batteries (ASSLMBs), yet these desired properties are rarely achieved simultaneously. Here, in this work, it is noticed that the huge resistance at Li metal/electrolyte interface dominantly impeded the normal cycling of ASSLMBs especially at around room temperature (<30 °C). Accordingly, a supramolecular polymer ion conductor (SPC) with “weak solvation” of Li + was prepared. Benefiting from the halogen‐bonding interaction between the electron‐deficient iodine atom (on 1,4‐diiodotetrafluorobenzene) and electron‐rich oxygen atoms (on ethylene oxide), the O‐Li + coordination was significantly weakened. Therefore, the SPC achieves rapid Li + transport with high Li + transference number, and importantly, derives a unique Li 2 O‐rich SEI with low interfacial resistance on lithium metal surface, therefore enabling stable cycling of ASSLMBs even down to 10 °C. This work is a new exploration of halogen‐bonding chemistry in solid polymer electrolyte and highlights the importance of “weak solvation” of Li + in the solid‐state electrolyte for room temperature ASSLMBs.