Preparation and characterization of high ionic conducting alkaline non-woven membranes by sulfonation

A novel method has been proposed for the preparation of alkaline, high ionic conducting membrane separators with lower cost using non-woven polypropylene/polyethylene (PP/PE) core-shell sheet membranes. Sulfonation was employed to enhance the membrane anionic conductivity by improved hydrophilicity and more amorphous structure of the polymer. The characteristic properties of these membrane separators have been studied by ac impedance, contact angle measuring system, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (IR), elemental analysis (EA), stress-strain test, X-ray diffraction (XRD) and scanning electron microscope (SEM). The incorporation of sulfonic acid groups in the polymer membranes was evidenced by the IR spectroscopy. The results showed that the sulfonation treatment reaction was very effective in increasing the surface hydrophilicity of the non-woven membranes. The suitable sulfonation process could increase the room temperature anionic conductivity of the membranes from 0.0088 to 0.0175 S cm^-1. The sulfonated membranes showed limited decline in thermal resistance (4%) and mechanical strength (21%). In addition, the further study on the solid-state zinc-air cells assembled from these membrane separators also exhibited an improved battery power density by 69%, from 16 to 27 mW/cm².