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 LiFePO₄ 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.