Microscopic phase-segregated quaternary ammonia polysulfone membrane for vanadium redox flow batteries

Anion-exchange membranes have been investigated for vanadium redox flow batteries. However, their commercial application is plagued by the low transportation efficiency of anions in the membranes. Inspired by a strategy for constructing an ionic highway in alkaline anion-exchange membranes to accelerate the migration of anions. Thus, a well-segregated phase morphology is achieved to construct three-dimensional anion channels via architectural design of amphiphilic quaternary ammonium polysulfone with hydrophobic hexane side chains. This unique morphology gives the membrane enhanced conductivity with less water uptake, and this thereby enables the vanadium redox flow battery that is fabricated with the microscopic phase-segregated membrane to have better voltage and energy efficiency under current densities in the range of 60–150 mA cm⁻². Furthermore, the vanadium redox flow battery using the microscopic phase-segregated membrane has excellent cycling stability. These investigations provide a universal strategy for developing of anion-exchange membranes that have high-conductivity and are stable for use in vanadium redox flow batteries.