Bio-Inspired Polydopamine-Modified ZIF-90-Supported Gel Polymer Electrolyte for High-Safety Lithium Metal Batteries

Gel polymer electrolytes (GPEs) with high ionic conductivity and good flexibility have emerged as promising alternatives to traditional liquid electrolytes. Metal–organic frameworks (MOFs), with a hierarchical pore structure and high porosity, have attracted widespread attention as high-performance solid electrolytes. However, severe agglomeration of MOF particles hampers Li+ transport, and the flammability of organic liquid electrolytes in GPEs poses safety risks. Herein, inspired by the bioadhesive properties of marine mussels, we developed novel polydopamine (PDA)-modified zeolitic imidazole framework-90 (ZIF-90) nanoparticles to act as a robust support layer. Based on the nonflammability and environmental friendliness of ionic liquids (ILs), through thiol–ene click chemistry, an IL-based gel is fabricated. PDA exhibits exceptional interfacial bonding between organic and inorganic components, thereby facilitating efficient Li+ transfer. The stable three-dimensional open framework of ZIF-90 anchors bulky ions of IL and lithium salt while allowing unrestricted movement of small Li+. The nanowetting interface formed by ZIF-90 and IL, along with the polyether segments on the gel backbone, further facilitates Li+ migration. The resulting ZIF-90@PDA GPE exhibits a high ionic conductivity of 2.98 × 10–4 S cm–1 at 30 °C and a lithium-ion transference number of 0.43. Moreover, enhanced suppression of lithium dendrite growth, along with notable thermal stability and flame retardancy is achieved. The assembled LiFePO4/Li cell demonstrates remarkable cycling performance, exhibiting an initial discharge capacity of 140 mAh g–1 at 30 °C and 0.5 C, with a capacity retention of 90% after 300 cycles.