Technology Outline (Process Description)

Ion exchange membranes are unique to many advanced energy devices. Their uniqueness comes from selectivity, permeability and ionic transport at elevated temperature and extremely oxidative environment. Their chemical and dimensional stability decides the specific device applications. We have made the ion-exchange membranes by melt cast extrusion of mass obtained from radical polymerization of styrene-divinyl benzene in molten polypropylene in xylene solvent followed by sulfonation with chlorosulfonic acid in dichloroethane. It results into the cation exchange membrane. The anion exchange membrane was prepared by radical polymerization of 4-vinyl pyridine-styrene-divinyl benzene in molten polypropylene in xylene solvent followed by quaternazation with methyl iodide in methanol. The developed membranes had excellent electrochemical and physicochemical properties induced from excellent chemical and mechanical stability of polypropylene matrix and controlled functionalization polystyrene/poly(4-vinyl pyridine). The vanadium redox flow battery assembled with cation exchange membrane showed the 98% columbic efficiency at 100 mA cm^-2 current density with 70 % voltage efficiency and 69 % energy efficiency in 500 charge/discharge cycles. The anion exchange membrane showed the best stability in alkaline water electrolysis to generate the hydrogen.