Tailoring Multiple Interactions in Poly (Urethane‐Urea)‐Based Solid‐State Polymer Electrolytes for Long‐Term Cycling Lithium Metal Batteries

Abstract Polyethylene oxide (PEO)‐based solid polymer electrolytes (SPEs) are considered as one of the most promising candidates for next‐generation lithium metal batteries. However, their application is limited by poor electrode/electrolyte interfacial stability, low Li‐ions transference number, and weak mechanical strength. Herein, poly (urethane‐urea)‐based SPEs are developed to enhance interfacial stability, improve Li‐ions transport kinetics, and provide superior mechanical properties. The poly (urethane‐urea) structure integrates abundant polar groups and rigid conjugated moieties, which facilitate interactions with the anions of lithium salt in SPEs, promoting the Li‐ions transference number and supporting the formation of a LiF‐rich solid electrolyte interphase (SEI) to guide uniform lithium deposition and suppress dendrite growth. Furthermore, a supramolecular crosslinked network is formed through multiple hydrogen bonds and π‐π stacking interactions, enhancing the mechanical strength and toughness of the SPEs. As a result, Li//Li solid‐state symmetric cells assembled with this SPE demonstrate stable cycling for over 3000 h, while LiFePO 4 solid‐state cells retain 93.6% of their initial capacity after 500 cycles at the rate of 1C. This work presents a feasible design strategy for developing highly functional SPE materials.