Crosslinkable Layer-by-Layer Assembled Sulfonated Poly(phenylene oxide) Membrane Based on Nafion for Vanadium Redox Flow Battery

Multilayered composite proton exchange membranes were prepared using the layer-by-layer (LbL) method by alternating the deposition of highly sulfonated poly(phenylene oxide) (sPPO) and cationic polystyrene copolymer electrolyte on the surface of Nafion 212. The cationic polystyrene copolymer contained an azide moiety. An anionic solution of sPPO containing 0.5 M NaCl was used to incorporate a thicker layer of sPPO. The membranes were crosslinked by using UV to provide an additional barrier property. Both uncrosslinked and crosslinked composite membranes showed decreased vanadium permeability as the number of bilayers increased and increased overall selectivity compared to Nafion (R) film.