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. La 2 O 3 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.