Nanoporous PVDF-HFP/PMIA Membrane with Heat-Resistance towards the Gel Polymer Electrolyte of Lithium Metal Batteries

Developing gel polymer electrolytes (GPEs) is a promising strategy to mitigate safety concerns caused by the leakage of liquid electrolytes in lithium metal batteries (LMBs). However, fabricating a membrane with high thermal stability, whose derived GPE also maintains good electrochemical performance, remains a major challenge. Herein, we report a composite membrane, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(m-phenylene isophthalamide) (PMIA), with excellent thermal stability and uniform nanoporous structure for high-performance GPE of LMBs. The PVDF-HFP/PMIA composite membrane, featuring a uniform pore size of 110 nm, is prepared by a double-sided solvent-nonsolvent exchange process via microfluidic technique. The incorporation of PMIA achieves the enhanced heat resistance of the composite membrane with a superior size retention of 86% after continuous heating at 250 °C for more than 360 min. The PVDF-HFP/PMIA GPEs-based Li||Li symmetric cells display stable voltage across various current densities and cycles for 600 h at 0.5 mA cm^-2. Moreover, the morphology of the lithium anodes after 100 h shows uniform lithium deposition, demonstrating excellent suppression of lithium dendrite growth. The Li||LFP cells assembled with PVDF-HFP/PMIA-based GPEs deliver a high discharge capacity of 134.5 mAh g^-1 at 5 C. The as-prepared heat-resistant GPEs membrane thus offers great potential for improving the safety performance of LMBs.