Study of ABPBI membrane as an alternative separator for vanadium redox flow batteries

Vanadium redox flow batteries are receiving great attention due to their capabilities of offering multiscale energy-storage and cross-contamination-free system. Ion-exchange membrane (IEM), which is one of the critical components in the vanadium redox flow battery (VRFB) system, simultaneously prevents the cross-mixing of active vanadium species, and facilitates the movement of the proton. The cross-mixing of the vanadium species influences coulombic efficiency (CE), whereas the proton movement influences the voltage and energy efficiency (EE). Hence, IEM plays a major role in the performance of the battery in terms of self-discharge rate, CE, crossover of active material, and ionic conductivity. In the present work, the suitability of an alternative low-cost, efficient, and durable membrane, which are essential for providing a sustainable solution for VRFB, is studied. 2,5-Polybenzimidazole membrane is studied as an alternative membrane and evaluated in a VRFB with mixed electrolyte, which has the potential to offer a substantial reduction in the cost. The mixed electrolyte helps in extending the operating temperature. 2,5-Polybenzimidazole membrane-based VRFB shows CE, EE, and voltage efficiency as 99%, 83%, and 84%, respectively, which is comparable to Nafion membrane.