Improved performance of PVdF-HFP/PI nanofiber membrane for lithium ion battery separator prepared by a bicomponent cross-electrospinning method

Abstract Poly(vinylidene fluoride-co-hexafluoropropylene)/polyimide (PVdF-HFP/PI) composite nanofiber membrane used for lithium ion battery separator was prepared by an electrospinning apparatus equipped with four needles. Two needles were fed with PVdF-HFP solution and the rest with PI solution and the two types of polymer solutions were arrayed alternately, in a straight line to form a composite membrane, which could be referred to as cross-electrospinning, followed by thermal calendering process to improve the mechanical property of the composite membrane via fusing the PVdF-HFP component which has lower melting temperature. PVdF-HFP/PI composite membrane showed positive results in terms of physical properties. Additionally, the cells assembled with the composite separators exhibited better electrochemical stability, lower interfacial resistance and higher ionic conductivity, compared with Celgard 2400 PP separator. Conspicuously, the improved performance of lithium ion battery separator indicated that bicomponent cross-electrospinning method could be potentially applied for designing future lithium ion battery separator.