A Polyurea-Crosslinked Gel Polymer Electrolyte for Solvation and Interphase Regulation in Lithium Metal Batteries

Polyurea (PUR) electrolytes offer molecular tunability, robust mechanics, and strong Li-salt affinity for lithium metal batteries, but their application is hindered by poor solubility, uncontrolled polymerization, and unstable Li/electrolyte interfaces. Herein, we report two polyurea-based polymerizable monomers with distinct functionalities, DPN and MPN, and construct flame-retardant polyurea gel polymer electrolytes (P-DPN and P-MPN) through an in situ polymerization strategy. This design simultaneously addresses solubility, electrolyte leakage, and interfacial instability. Mechanistic investigations reveal that the carbonyl groups in the urea moieties coordinate with lithium ion (Li⁺) to homogenize lithium deposition, while the -NH groups interact with anions to induce weakly solvated Li⁺ structures, thereby accelerating ion transport. Meanwhile, the low HOMO energy level of the polyurea framework promotes the formation of a robust LiF/Li₃N-rich inorganic solid electrolyte interphase (SEI), effectively suppressing parasitic reactions and dendrite growth. As a result, the Li||P-MPN||Li symmetric cell exhibits stable cycling for over 2300 h, and full cells paired with diverse cathodes (including NCM811, LCO, and LFP) exhibit outstanding cycling stability under high cathode loading and even at -20°C. This work establishes a molecular design strategy for in situ polyurea electrolytes and deepens the understanding of solvation/interphase regulation in high-performance and safe lithium metal batteries.