A robust bi-layer separator with Lewis acid-base interaction for high-rate capacity lithium-ion batteries

Poly(vinylidene fluoride-hexafluoropropylene)-lanthanum oxide//poly(vinylidene fluoride-hexafluoropropylene)-hexagonal boron nitride (PVH–LaO//PVH-BN) bi-layer separators are developed through a two-step blading approach. La₂O₃ in the PVH matrix enhances the Li⁺ conduction by providing extra Li⁺ conducting pathways owing to the Lewis acid-base interaction of La atoms with the PVH chains, leading to a high lithium-ion transference number of 0.72 and ionic conductivity of 7.5 × 10⁻⁴ S cm⁻¹ at room temperature. Moreover, the strong interfacial interaction between h-BN and PVH in the bi-layer separator enhances the thermal and mechanical stabilities of the separator. Batteries based on lithium iron phosphate and the bi-layer separator deliver a discharge capacity of 158 mAh g⁻¹ at 0.5 C after 100 cycles and a rate capacity of 81 mAh g⁻¹ at 10 C after 1500 cycles.