Novel polyolefin based alkaline polymer electrolyte membrane for vanadium redox flow batteries

Abstract

Low conductivity and stability of anion exchange membranes limited the durability and performance of corresponding fuel cells despite their unique advantages in compared to the proton exchange membrane fuel cells. In this work, we present a simple and efficient method to fabricate highly durable anion exchange membranes from commercial porous hydrocarbon substrates. Polyethylene/polypropylene (PE/PP) microfibers is employed as a substrate and radiation induced emulsion grafting is utilized to introduce poly(vinylbenzyl chloride) side chains. The grafted substrates with flexible content of side chains are converted to anion exchange membranes by converting into dense membranes and introducing quaternary amine groups. The dense membranes are characterized and employed in vanadium redox flow battery (VRFB) application. Developed membranes demonstrate high anion conductivity, low vanadium permeability and good chemical and mechanical stability. In compare to Nafion 117, superior performance is achieved for the developed membranes as the undesired vanadium ion permeability is reduced by 16 times and the energy efficiency significantly enhanced by 9% at current density of 80 mA cm−2. Such enhanced performance of the developed membrane is attributed to the presence of positive charged ionic groups in the membrane structure.