Abstract To develop cost-effective membranes with low permeability of vanadium ions for vanadium redox flow battery (VRB) application, an inexpensive precursor membrane material, chloromethylated poly(phthalazinone ether ketone ketone), is first prepared from poly(phthalazinone ether ketone ketone) with nitrobenzene as the solvent, and then reacted with trimethylamine to form quaternized poly(phthalazinone ether ketone ketone) (QAPPEKK) anion exchange membranes. At an ion exchange capacity of 1.56 mmol g −1 , the QAPPEKK membrane shows much lower permeability of vanadium ions (0.17 × 10 −4 cm min −1 for V 3+ and 0.21 × 10 −4 cm min −1 for VO 2+ ) than that of Nafion117 membrane (1.34 × 10 −4 cm min −1 for V 3+ and 1.19 × 10 −4 cm min −1 for VO 2+ ), resulting in higher coulombic efficiency (99.4% at 80 mA cm −2 ). In addition, the energy efficiency of the VRB with QAPPEKK membrane is comparable to that of VRB with Nafion117 membrane. Moreover, the QAPPEKK membrane is stable in VO 2 + electrolyte, and exhibits good performance in the 100-cycle charge-discharge test of VRB.