Phosphorus flame retardant modified aramid nanofiber separator for advanced safety lithium-sulfur batteries

Safety concerns have perennially impeded the large-scale implementation of high-energy-density storage systems. Nevertheless, because the intrinsic drawbacks of the commercial polyolefin separator are poor thermal stability and low flammability with a large thermal contribution, the development of an advanced separator that solves the above questions is imminent. In this work, gradient flame-retardant aramid nanofiber separators (T-PMIA) were synthesized by a single-step electrospinning method. Benefiting from the feature of "Aramid" fibers, plentiful multilevel beaded structure and the functional groups P and -P-O, the T-PMIA separator not only guarantees a rapid self-extinguishing feature (self-extinguishing time: 0.20 s) and impressive mechanical properties (tensile strength of up to 12.58 MPa and puncture force of 0.94 N) but also effectively suppresses the polysulfide shuttle and lithium dendrite growth. Accordingly, the T-PMIA separator still showed a stable cycling performance (maintain 901.7 mAg−1 after 100 cycles) even at high temperature (80 °C). This simple separator strategy offers a highly competitive option for the large-scale production of high-safety lithium-sulfur (LiS) batteries.