A nano-silica/polyacrylonitrile/polyimide composite separator for advanced fast charging lithium-ion batteries

In this work, composite separators were fabricated based on silica particles embedded in polyacrylonitrile and polyimide. The efficient and cost-effective electrospinning technique was used, followed by thermal pressing. The results demonstrate that the electrospun composite separator membranes have high thermal stability and high tensile strength, which can effectively improve battery safety. Furthermore, compared with a commercial Celgard separator, the composite separator membranes have better affinity towards liquid electrolyte, higher porosity and lower internal resistance in the transportation of ions between electrodes, leading to stable cyclability and superior C-rate capacity. The highest discharge capacity of 147 mAh.g−1 was obtained at a current rate of 1C with coin cells assembled with separator CS-3 (10 wt% silica (SiO2), 5 wt% 4,4′-oxydianiline (ODA), 5 wt% pyromellitic dianhydride (PMDA), and 10 wt% polyacrylonitrile (PAN) in dimethylformamide (DMF)). Furthermore, the capacity retention was 93% after 200 cycles of charging and discharging.