A novel amphoteric ion exchange membrane synthesized by radiation-induced grafting α-methylstyrene and N,N-dimethylaminoethyl methacrylate for vanadium redox flow battery application

Abstract

Abstract A novel amphoteric ion exchange membrane (AIEM) was synthesized by radiation-induced grafting α-methyl styrene (AMS) and dimethylaminoethyl methacrylate (DMAEMA) into poly(vinylidenedifluoride) (PVDF) films, followed by sulfonation and protonation processes. The monomer AMS could be co-grafted successfully with DMAEMA in the presence of AlCl 3 although it was difficult for AMS to be grafted solely into PVDF films. The grafting yield ( GY ) increased with absorbed dose up to about 40 kGy. It was found that the ratio of DMAEMA to AMS in the poly(DMAEMA- co -AMS) grafts changed slightly with various monomer ratio of DMAEMA to AMS in the feed by elemental analysis. The Micro-FTIR and XPS analyzes testified that the AIEM had been prepared as designed. The AIEM with a GY of 40% showed similar conductivity, higher IEC and lower permeability of vanadium ions compared with Nafion117 membrane. The vanadium redox flow battery (VRFB) assembled with the AIEM of 41.1% GY maintained an open circuit voltage higher than 1.4 V after placed for 60 h, which was much longer than that with the Nafion117 membrane. Therefore, it is expected to be excellent candidate for the application of VRFB.