A detachable sandwiched polybenzimidazole-based membrane for high-performance aqueous redox flow batteries

A cost-effective membrane is critical for commercialization of aqueous redox flow batteries (ARFBs). In this work, we design and fabricate a membrane composed of a thin polybenzimidazole (PBI) dense film physically sandwiched by two polyacrylonitrile (PAN) electrospun nanofiber layers. The thin PBI dense film (7 mu m thick) simultaneously diminishes its area resistance and retains its innate ultrahigh ion selectivity, while the hydrophilic PAN porous layers (10 mu m thick on each side) reinforce and protect the thin PBI dense film. As a result, the composite membrane enables a vanadium redox flow battery, one of the most promising ARFBs, to achieve a coulombic efficiency (CE) of 99.8% and an energy efficiency (EE) of 80.7% at the current density of 300 mA cm-2, surpassing the efficiencies using the commercial Nafion 211 membrane (CE-97.7%, EE-78.6%) and representing one of the best performances of the batteries using composite membranes in the open literature. More importantly, our detachable sandwiched design allows facile fabrication and wide choices of supporters, thereby providing more opportunities for the development of low-cost and high-efficiency membranes for ARFB applications.

Automated summary

This study introduces a cost-effective membrane design for aqueous redox flow batteries, achieving higher coulombic efficiency and energy efficiency compared to commercial Nafion 211 membrane.