Novel sulfonated polyimide/ZrO2 composite membrane as a separator of vanadium redox flow battery

Sulfonated polyimide (SPI) and ZrO2 are blended to prepare a series of novel SPI/ZrO2 composite membranes for vanadium redox flow battery (VRFB) application. Results of atomic force microscopy and X-ray diffraction reveal that ZrO2 is successfully composited with SPI. All SPI/ZrO2 membranes possess high proton conductivity (2.96-3.72x 10(-2) S cm(-1)) and low VO2+ permeability (2.18-4.04x 10(-7) cm(2) min(-1)). SPI/ZrO2 -15% membrane is determined as the optimum one on account of its higher proton selectivity and improved chemical stability. The VRFB with SPI/ZrO2-15% membrane presents higher coulombic efficiency and energy efficiency than that with Nafion 117 membrane at the current density, which ranged from 20 to 80 mA cm(-2). Cycling tests indicate that the SPI/ZrO2-15% membrane has good operation stability in the VRFB system. Copyright (c) 2014 John Wiley & Sons, Ltd.