Quaternized poly(phthalazinone ether ketone ketone) anion exchange membrane with low permeability of vanadium ions for vanadium redox flow battery application

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 V3+ and 0.21 × 10−4 cm min−1 for VO2+) than that of Nafion117 membrane (1.34 × 10−4 cm min−1 for V3+ and 1.19 × 10−4 cm min−1 for VO2+), 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 VO2+ electrolyte, and exhibits good performance in the 100-cycle charge-discharge test of VRB.

► CMPPEKK was first prepared with nitrobenzene as solvent.
► QAPPEKK membrane showed low vanadium ions permeability.
► QAPPEKK membrane in VRB showed high columbic efficiency.
► QAPPEKK membrane was stable in VO2+ electrolyte.
► QAPPEKK membrane showed stable performance in VRB cycling test.