Multiple hydrogen bonds enable an ultra-rapid self-healing polymer electrolyte for high-performance lithium-metal batteries

Polymer electrolytes possessing rapid self-healing rate and high ionic conductivity are critically needed for enhancing the interfacial durability and cycling stability of solid-state lithium metal batteries (SSLMBs). Herein, a novel self-healing polymer electrolyte (SHPE) with a unique three-dimensional (3D) cross-linked network was fabricated via thermal-initiated radical polymerization. The incorporation of ethoxylated trimethylolpropane triacrylate (ETPTA) monomers, which contain abundant flexible ethoxy chains (–CH₂–CH₂–O–) and strongly polar carbonyl (C=O) groups, facilitates enhanced segmental mobility and enables precise modulation of the cross-linking density effectively. Benefiting from this synergistic effect, the novel SHPE exhibits an impressive ionic conductivity of 9.07 × 10⁻⁴ S·cm⁻¹ at 60 °C, rapid self-healing capability (within 30 min), and high lithium ion transference number (0.66). Consequently, the Li||Li symmetrical cells assembled with the optimized electrolyte system UEP17.5-SHPE (UEP17.5 refers to ureidopyrimidinone-ETPTA (17.5 wt.%)-poly(ethylene glycol), denoted as UPy-ETPTA17.5-PEG) achieve ultra-long cycling performance (over 4000 h). Furthermore, the SSLMBs employing lithium iron phosphate (LFP) cathode and UEP17.5-SHPE exhibit a high capacity retention of 80% after 400 cycles at 1 C. Crucially, systematic analysis confirms that the self-healing process does not compromise these electrochemical performances. This work provides a viable strategy for designing high-performance SHPEs toward practical SSLMBs.