Coaxially electrospun PAN/HCNFs@PVDF/UiO-66 composite separator with high strength and thermal stability for lithium-ion battery

Various methods have been used to improve mechanical and thermal performance of electrospun separators in order to implement or scale up their application in batteries. Here a combination of organic & inorganic doping, hot-pressing and coaxial electrospinning technique is employed to develop a core@shell - PAN/HCNFs@PVDF/ UiO-66 - composite membrane (PAN: polyacrylonitrile, HCNFs: helical carbon nanofibers, PVDF: poly (vinylidene fluoride), UiO-66: a Zr-based Metal-Organic Framework). The core@shell structure is demonstrated in the electrospun fibers. With the synergetic effect of hot-pressing and the PAN/HCNFs core layer, the fiber membrane can stand tension up to 24.77 MPa. The core layer also helps the electrospun membrane keep intact profile at 200 degrees C. Besides the HCNFs can support the fibers without serious shape change during the hot-pressing treatment, facilitating retention of high porosity (77.61%). The PVDF/UiO-66 shell layer provides good affinity to electrolyte causing excellent electrochemical performance of lithium ion batteries with the composite membranes.