Nano-tube TiO2 composite PVdF/LiPF6 solid membranes

Nano-tube TiO2 enhances ion conductivity of poly (vinyldene fluoride) (PVdF)/LiPF6 polymer electrolyte. Complexation structure and the lithium ion conductivity of the composite are examined. The X-ray photoelectron spectroscopy (XPS) C1s and F1s spin–orbital splitting photoelectrons spectrum of pure PVdF change enormously with the addition of the lithium salt and nano-tube TiO2. The results are consistent with a structure that the fluorine atoms in PVdF and oxygen atoms in inorganic oxide TiO2 are coordinating with the dissociated Li+ ions through acid–base interactions. The association hinders PVdF crystallization and reduces the crystallite size. This also changes the surface potential of PVdF and offset the sol dimension during film formation, confirmed by scanning electron microscopy (SEM). Such interactions explain miscibility between PVdF and nano-tube TiO2 is improved by the lithium salt. Compared to pure PVdF/LiPF6 electrolyte, the one order enhancement of ion conduction in nano-tube TiO2 composite polymer electrolyte is believed to have originated from the new ion conduction mechanism on TiO2 tube surface.