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

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.