Hydrophilic porous poly(sulfone) membranes modified by UV-initiated polymerization for vanadium flow battery application

Hydrophilic porous poly (sulfone) (PSF) membranes were prepared and first employed in vanadium flow battery (VFB) operation. In this study, sodium p-styrene sulfonate (NaSS) was grafted on PSF phase inversion membranes by UV-initiated vinyl monomer polymerization. The grafting degree (GD) of PSF membranes was adjusted via controlling the wavelength of ultraviolet light, the concentration of photo-initiator and the irradiation time. The effect of GD on the membranes' hydrophilicity as well as their performance in VFB was studied in detail. It was proved that under the given condition, longer UV-irradiation time could induce membranes with higher GD, which led to more hydrophilic membranes. Under VFB operating condition, the membranes exhibited lower area resistance and higher ions permeability. As a result, the VFBs fabricated with the membranes showed relatively high voltage efficiency and low columbic efficiency. The membranes with controlled performance in VFB can be realized via adjusting their hydrophilicity.