Poly(phthalazinone ether ketone) amphoteric ion exchange membranes with low water transport and vanadium permeability for vanadium redox flow battery application

Compact and homogeneous amphoteric ion exchange membranes (Q/S-AIEMs) without acid–base interaction for vanadium redox flow batteries (VRBs) are first prepared through a low-cost and simple way, in which the amounts of different ion exchange groups are controllable in a wide range. Brominated poly(aryl ether ketone) containing 3,5-dimethylphthalazinone moieties (BPPEK) and sulfonated poly(phthalazinone ether ketone) (SPPEK) are mixed forming into a series of blended base membranes. Q/S-AIEMs are prepared through the quaternary amination of the blended base membranes. Based on different effects of divided quaternary ammonium groups and sulfonic groups on vanadium permeability, the relative magnitude of the permeability of different vanadium species could be changed, and the net water transport volume across Q/S-AIEMs is reduced by varying ion exchange group loading, and these are first discussed. At 30% SPPEK, the static and cycling water transport volume across the Q/S-AIEM is 96.0% and 87.8% less than Na...