Polyvinylidene fluoride/polystyrene hybrid fibers with high ionic conductivity and enhanced mechanical strength as lithium-ion battery separators

Ionic conductivity is an important separator parameter influencing the cycle life and rate capability of lithium-ion batteries (LIBs). To improve the ionic conductivity of polyvinylidene fluoride (PVdF) fibers, polystyrene (PS) was added into the PVdF electrospinning solution for the fabrication of PVdF/PS hybrid fibers. The morphology and electrochemical property were regulating by tuning the PS dosage. Owing to the increasing mass ratio of the adhesion structure, not only the porosity, uptake, and average pore size of PVdF/PS hybrid fibers simultaneously decreased but also the mechanical strength enhanced (15.9 MPa) with the increasing PS content. In addition, the ionic conductivity increased with increasing PS content (1.58 mS cm−1 for PVdF/PS hybrid fiber with 20-wt% PS) ascribing to the increase of the amorphous region. Benefiting from the characteristic of PVdF, the as-prepared PVdF/PS hybrid fibers with non-flammability can significantly improve the LIBs safety. Significantly, the cells with PVdF/PS hybrid fibers (15-wt% PS) displayed satisfactory cycling performance (159.9 mAh g−1 at 0.2 C for 45 cycles after testing at 0.1 C for 5 cycles) and rate capability, indicating that PVdF/PS hybrid fibers are the promising separator candidates for the applications in LIBs.