LAUSR

Abstract In this paper, the composite membranes based on poly(vinylidene fluoride) (PVDF) with different amounts of halloysite (HNT) nano-filler were prepared by phase inversion method for the application of lithium ion batteries. The effect of the content of HNT on the crystallinity and morphology of the composite membranes were investigated. The results showed that the crystallization behaviors of the HNT/PVDF composite membranes were reduced with the increase of HNT filler content. Furthermore, the introduction of HNT into PVDF matrix remarkably affected the formation rate of nuclei which could evolve into pores to change surface morphology. The HNT/PVDF composite membranes showed the sufficient porosity and good affinity between the eletrolyte as well as the electrode, which led to superb electrolyte uptake and low interfacial impedance. Among HNT/PVDF composite membranes, in particular, the 4-HNT/PVDF composite membrane with 4 wt% HNT content had a great electrolyte uptake (430.2%), superior electrochemical stability window (4.5 V), high ionic conductivity (2.4 mS/cm), and low interfacial impedance (63Ω). The cells assembled with the 4-HNT/PVDF composite membranes obtain discharge capacities of 164.72 mAh/g (0.1C) and 134.88 mAh/g (2C), corresponding to 96.89% and 79.34% of the theoretical capacity of LiFePO4 (170 mAh/g), respectively, better cycle performance (with capacity retention 89.12% after 100 cycles) at 0.5C and excellent rate performance. It is concluded that the content of HNT deeply affects membrane performance. Therefore, the 4-HNT/PVDF composite membranes could be a good option of high performance lithium ion batteries.