Advanced Sulfonated Poly(Ether Ether Ketone)/Graphene-Oxide/Titanium Dioxide Nanoparticle Composited Membrane with Superior Cyclability for Vanadium Redox Flow Battery

The purpose of this study was to improve the repulsion ability of sulfonated poly(ether ether ketone) (SPEEK) membrane for the vanadium ions crossover. For this purpose graphene oxide (GO) nanosheet and titanium dioxide (TiO2) nanoparticles were employed into the polymer matrix to prepare SPEEK/GO/TiO2 hybrid membrane via solution-casting method for vanadium redox flow battery (VRFB). The morphology, permeability of vanadium ions and device performance of as prepared membrane were investigated and discussed. It was observed that with the barrier block effect by the filler, the VRFB single cell with the optimized SPEEK/GO/TiO2 hybrid membrane exhibited high coulombic efficiency (similar to 99%), excellent energy efficiency (similar to 85%) and vigorous cyclability (similar to 97.2% capacity retention after 100 cycles). Moreover, the VRFB cell with this blend membrane showed lower vanadium ions permeability than Nafion 212 or pure SPEEK membranes. These results demonstrated that the comprehensive properties of hybrid membrane have been remarkably improved comparing to pristine SPEEK which suggested that the hybrid membrane was applicable for VRFB energy storage system.