A 3D-dimensional interconnected structured poly (m-phenylene isophthalamide) nanofiber separator with Li_1.5Al_0.5Ge_1.5(PO₄)₃ for high-safety lithium-sulfur batteries

Safety concerns have consistently presented substantial obstacles to the widespread adoption of lithium-sulfur (Li-S) batteries. Conventional polyolefin separators, which are characterized by low flash points and insufficient mechanical strength, pose potential safety hazards, including risks of fire and explosion under extreme operating conditions. In this study, we introduce a thermally stable and non-flammable poly-m-phenyleneisophthalamide (PMIA)-based multifunctional separator (L-PMIA separator), which is enhanced with lithium aluminum germanium phosphate (Li_1.5Al_0.5Ge_1.5(PO₄)₃ or LAGP) fillers. By incorporating g high-ionic-conductivity LAGP and establishing an interconnected framework, this design effectively mitigates the issues of particle agglomeration and uneven commonly ion transport associated with traditional separators. The L-PMIA separator demonstrates remarkable mechanical strength (with a tensile strength of 8.5 MPa and a puncture force of 0.72 N) and thermal stability (showing no dimensional shrinkage even at 200 °C), while also facilitating the formation of continuous ion channels that inhibit lithium dendrite growth. Consequently, Li-S batteries utilizing the 4L-PMIA separator demonstrated a reversible capacity of 4.97 mAh cm⁻² after 150 cycles, even under conditions of high sulfur loading (6.75 mg cm⁻²), limited electrolyte availability (E/S = 7), and elevated temperatures. This approach offers novel insights for the development of future energy storage systems characterized by enhanced safety and performance.