Thin Film Nanocomposite Membrane Incorporated With Hydroxylated Hexagonal Boron Nitride for Vanadium Redox Flow Battery

ABSTRACT In order to improve the selectivity of the porous membrane for vanadium redox flow battery (VRB), a thin film nanocomposite (TFN) membrane is constructed by incorporating hydroxylated hexagonal boron nitride into the skin layer of the polyether sulfone/sulfonated polyether ether ketone porous substrate ( M 0 ) via the interfacial polymerization method. By employing the stable polyethyleneimine and cyanuric chloride monomers, the as‐prepared TFN membrane not only exhibits high selectivity but also high stability for VRB application. As a result, the VRB assembled with the optimized MB 0.6 TFN membrane shows the highest coulombic efficiency (CE) of 99.3% at a current density of 80 mA cm −2 , and the highest EE (energy efficiency) of 88.4% at a current density of 40 mA cm −2 . As a comparison, at the same current density, the CE and EE of the VRB assembled with M 0 are only 90.0% and 73.2%, respectively, and the CE and EE of the VRB assembled with commercial Nafion 115 are 91.7% and 73.8%, respectively. Furthermore, the MB 0.6 membrane presents stable cell performance with no significant decay of cell efficiencies during a 100 cycles test. The results indicate that the composite membrane with high selectivity and stability has potential as an alternative to Nafion in VRB application.