Preparation and characterization of sulfonated polyimide/TiO2 composite membrane for vanadium redox flow battery

A sulfonated polyimide (SPI)/TiO2 composite membrane was fabricated by a blend way to improve its performance in vanadium redox flow battery (VRB). Both EDS and XRD results verify the successful preparation of the SPI/TiO2 composite membrane. The surface SEM image shows its homogeneous structure. TG analysis identifies its thermal stability. The SPI/TiO2 composite membrane possesses much lower permeability of VO2+ ions (2.02 x 10(-7) cm(2) min(-1)) and favorable proton conductivity (3.12 x 10(-2) S cm(-1)). The VRB single cell with SPI/TiO2 composite membrane shows higher coulombic efficiency (93.80-98.00 %) and energy efficiency (83.20-67.61 %) at the current density ranged from 20 to 80 mA cm(-2) compared with that with Nafion 117 membrane. And the operational stability of the as-prepared composite membrane is good after 50 times of cycling tests. Therefore, the low-cost SPI/TiO2 composite membrane with excellent battery performance exhibits a great potential for application in VRB.