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 (2.96–3.72 × 10^?2 S cm^?1) and low VO²⁺ permeability (2.18–4.04 × 10^?7 cm² 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 © 2014 John Wiley & Sons, Ltd.