PVDF-based micro inorganic fillers-containing polymer electrolyte membranes

Polymer electrolyte membranes based on poly (vinylidene fluoride-co-hexafluoropropylene) (PVDFHFP) with and without different types of micro inorganic fillers were prepared by phase-inversion process. Morphologies, porosities and electrochemical properties of the as-prepared membranes were investigated by means of scanning electronic microscopy (SEM), PC (propylene carbonate) uptake and alternating current (AC) impedance technique. Compared with other membranes, the membrane with micro SiO₂ filler shows a dense morphology so that its PC uptake is the highest, namely, 339%. The membrane filled with micro TiO₂ exhibits good electrochemical performances: the ion conductivity is as high as 1.1 × 10^-3 S/cm at 18°C, which can meet the demand of lithium ion batteries. Moreover, its initial charge-discharge efficiency exceeds 89%. The composite membranes with micro SiO₂, TiO₂ and Al₂O₃ are more suitable for the utilization in lithium ion batteries due to better cycleability, whereas the battery assembled with the blank membrane containing no inorganic fillers encounters a short circuit after the 5th cycle.