Preparation and electrochemical characterization of electrospun, microporous membrane-based composite polymer electrolytes for lithium batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) {P(VdF-HFP)} membranes incorporating 0, 6 and 10 wt.% of nano-meter sized particles of SiO2 were prepared by electrospinning. These membranes served as host matrix for the preparation of polymer electrolytes (PEs) by activating with the non-volatile and safe room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) (BMITFSI). The membranes consisted of layers of fibers with average fiber diameter of 2–5 μm and had a porosity of~ 87%. PEs with SiO2 exhibited higher ionic conductivity with a maximum of 4.3 × 10−3 S cm−1 at 25 °C obtained with 6% SiO2. The optimum PE based on the membrane with 6% SiO2 exhibited better compatibility with lithium metal electrode on storage and resulted in enhanced charge–discharge performance in Li/LiFePO4 cells at room temperature, delivering the theoretical specific capacity of 170 mAh g−1 at 0.1 C-rate. The PEs exhibited a very stable cycle property as well, demonstrating their suitability for lithium battery applications.