Enhanced Treatment of Electrospun PVDF-HFP/PMIA Fiber Membrane as Separators for Lithium-Ion Batteries

Abstract

In this study, electrospinning Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fiber membrane for lithium-ion battery separator was prepared by simultaneous electrospinning and coaxial electrospinning. The membranes were treated using acetone under different temperature and time to increase the strength and stability of membrane. The surface morphology, porosity, electrolyte uptake, heat stability were studied in details. The electrochemical performance of samples was tested as a separator in the lithium-ion battery. The results showed that the composite fiber membrane with sheath/core structure exhibited better performance than that of the membrane prepared by simultaneous electrospinning. The heat shrinkage rate of sheath/core structure fiber membrane was 2.2 % at 150℃, electrolyte uptake was 490 % and the tensile breaking strength was 13.21MPa. The sheath/core structure fiber membrane ionic conductivity at room temperature was 2.87x10-3 S/cm, the electrochemical stability window was 5.3 V, and showed capacity of about 169.5 mAh/g at 0.2 C. After 100 charging and discharging cycling, the specific capacity retention rate of battery was 99 %. The obtained results suggest that PVDF-HFP/PMIA coaxial electrospun membrane can be used as separator for high performance lithium-ion battery.