Imidazole-Functionalized Polyamide Lithium Ion-Solvating Membranes: A Molecularly Engineered Quasi-Solid Electrolyte for High-Performance Lithium Metal Batteries

Lithium ion-solvating membranes (ISMs) enable Li + transport in lithium metal batteries (LMBs) by absorbing electrolytes to form a stable polymer/electrolyte/lithium salt ternary coordination system. Herein, we report flame-retardant aromatic polyamide ISMs incorporating 2-(3-aminophenyl)-5-aminobenzimidazole (PABZ) moieties, fabricated by blending with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and through subsequent electrolyte activation to form a quasi-solid system. The imidazole units synergistically mediate Li + solvation via cooperative coordination with LiTFSI while constructing hydrogen-bond networks, as confirmed by NMR and Raman spectroscopy. This dual mechanism concurrently enhances LiTFSI dissociation efficiency and mechanical robustness while stabilizing electrode-electrolyte interfaces. The optimized PABZ-20-ISM shows excellent thermal stability up to 300 °C, a tensile strength of 11.8 MPa and an elongation at break of 94.5%. The resulting membrane exhibits exceptional room-temperature ionic conductivity (2.46 × 10 -3 S cm -1 ), a high Li + transference number (0.8), and an electrochemical stability window that extends to 5.18 V. Its inherent flame-retardant properties and dendrite-suppressing capability enable the Li||PABZ-20-ISM||Li symmetric cell to cycle stably for over 1000 hours at 0.1 mA cm -2 . Meanwhile, the LFP||PABZ-20-ISM||Li half-cell delivers 160 mAh g -1 at 0.5C, retains 88.3% of its capacity over 500 cycles, and fully recovers capacity when reverted to 0.1C. By integrating ionic transport efficiency, interfacial stability, and thermal safety, this molecularly engineered electrolyte design provides a transformative solution for high-performance lithium metal batteries.