ZIF-8-Functionalized Flame-Retardant and Elastic PAN Separator for High-Safety Lithium–Sulfur Batteries

With a theoretical specific capacity of 1675 mAh·g –1 and an energy density approaching 2600 Wh·kg –1, lithium–sulfur (Li–S) battery chemistry occupies a unique position among emerging electrochemical energy storage technologies. The primary challenge faced by current (LSBs) is to enhance energy density while ensuring safety. To address these challenges, we developed a PAN@ZIF-8 composite separator by assembling zeolitic imidazolate framework-8 (ZIF-8) on electrospun polyacrylonitrile (PAN) nanofibers. This separator effectively reduces the shuttle effect of Li 2 S n through a combination of ZIF-8’s pore sieving and chemical anchoring at the zinc sites. The PAN@ZIF-8 separators exhibit an initial discharge capability of 1154.84 mAh·g –1 at 0.2C and maintain excellent cycling stability after 100 cycles, with a Coulombic efficiency exceeding 98.3%. The PAN@ZIF-8 battery has good rate performance. Upon stepping the current density back down to 0.2C, the PAN@ZIF-8 cell recovered a reversible capacity of 686.54 mAh·g –1 . Compared with PP and PAN separators, the attenuation rate is lower. Furthermore, the tensile strength of the PAN@ZIF-8 separator reaches 12 MPa and the breaking strain exceeds 15%. Compared with the PAN separator, the tensile strength deformation increases by 20%. Meanwhile, due to the high ignition point and good thermal conductivity of ZIF-8, the flame retardant performance of the separator has been enhanced. The PAN@ZIF-8 separator cannot be ignited under an alcohol flame with a temperature higher than 300 °C. This research offers an effective strategy to overcome the safety and cycling stability issues of Li–S batteries and paves the way for the development of high-performance key components for advanced Li–S batteries.