Preparation of Polyvinylidene Chloride Composite Separator with Flame Retardant Properties

Abstract In commercialized lithium-ion batteries, polyolefin separators are widely used despite their inherent drawbacks, including poor thermal stability and inadequate electrolyte wettability. These issues prevent them from meeting the criteria for safety and rapid charging/discharging performance. Through the application of the solution casting method in air, polyvinylidene chloride (PVDC) is used as the polymer matrix material, and lithium salt is added to prepare a separator that exhibits excellent oxygen-barrier and wetting properties. Moreover, the incorporation of sodium hexafluoroantimonate and triglycidyl isocyanurate promotes the cross-linking of PVDC. As a result, its porosity (up to 65%), liquid absorption (up to 350%), tensile strength, and elongation at break are improved. The resulting composite separator exhibits outstanding flame-retardant properties, including a high thermal shrinkage temperature of 180 °C. The half-cell buckle test reveals that the capacity and cycling performance of LiFePO4 are also significantly enhanced, achieving a high-rate discharge-specific capacity of 140 mAh/g at 5 C. This study offers valuable insights for the development of high-safety lithium-ion battery separators with flame-retardant features.