Ionic conductivity and diffusion coefficient studies of PVdF–HFP polymer electrolytes prepared using phase inversion technique

A novel polymer membrane comprising poly(vinylidene difluoride hexafluoropropylene) (PVdF–HFP) copolymer was prepared by phase inversion technique with two different nonsolvents. The membranes were gelled in an electrolyte solution of 1 M of LiPF6 in EC/DMC and were subjected to a.c. impedance analysis at temperatures ranging from −30 to 70 °C. The films were characterized by SEM, adsorption/desorption, NMR spectroscopy and charge–discharge studies. The morphology, pore diameter, pore volume, and the ionic conductivity of the films varied greatly with the nonsolvent. The diffusion coefficients of 7Li and 19F ionic species were separately identified using the pulsed-field gradient NMR (PFG-NMR) and the results are discussed. The morphology and other physical properties of the films are correlated with the structure of the nonsolvent used.