Preparation and characterization of the side-chain quaternized poly(phthalazinone ether ketone)s with phenyl groups for vanadium redox flow battery

Abstract A series of new side-chain substitution poly(phthalazinone ether ketone)s with benzyl chloride moieties (CMPPEK-P) were synthesized through the chloromethylation of poly(aryl ether ketone)s containing pendant phenyl groups (PPEK-P). The content of side-chain phenyl groups in the PPEK-P was controlled by the feed ratios of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-ketone to 4-(3-phenyl-4-hydroxyphenyl)-2,3-phthalazin-1-ketone during polymerization process. The chemical structures of PPEK-P and CMPPEK-P were assessed by 1H NMR and FTIR spectroscopy. Based on the characterization results, a new anion exchanged membrane (QAPPEK-P) was prepared by amination reaction used for vanadium redox flow batteries. The ion-exchange capacity of QAPPEK-P membranes (0.21–0.88 mmol g−1) was related to the content of side-chain phenyl groups. The cell performance of QAPPEK-P membrane was increased with the increasing values of IEC. Compared with Nafion 115, QAPPEK-P-50 displayed higher voltage efficiency (82.8% vs. 76.9%) and energy efficiency (80.2% vs. 76.5%) at the current density of 140 mA/cm2. Furthermore, the efficiencies of QAPPEK-P-50 remained stable for 150 cycles and there was no obvious change in its structure.