High‐Performance PE‐BN/PVDF‐HFP Bilayer Separator for Lithium‐Ion Batteries

Abstract Highly efficient and thermally stable polyethylene‐hexagonal boron nitride/poly(vinylidene fluoride‐hexafluoropropylene) (PE‐BN/PVDF‐HFP) bilayer separator with microporous structure is prepared, for the first time with a wet chemistry method. The incorporation of hexagonal boron nitride particles in PE matrix promotes the interfacial interaction between PE and PVDF‐HFP layers to prevent separation of layers and supresses dendrite growth owing to the strong adsorption energy with polymers, large interactive surface area, and superior mechanical capability. The PVDF‐HFP layer provides additional thermally stable backbone while its inherent hydrophilic property and highly porous structure improve the overall performance of the separator. The bilayer separator owns a high electrolyte uptake of 348% and a thermal shrinkage of 6.6% upon annealing at 140 °C for 1 h. The lithium iron phosphate/lithium cell with the as‐prepared separator owns a high ionic conductivity up to 4.4 × 10 −4 S cm −1 , and a room‐temperature capacity of 120 mAh g −1 at 2 C with a 95% capacity retention after 500 cycles and a capability of 108 mAh g −1 at 4 C. The PE‐BN/PVDF‐HFP separator is a promising alternative of traditional multilayer separators for high‐performance lithium‐ion batteries.