Polyvinylpyrrolidone-based semi-interpenetrating polymer networks as highly selective and chemically stable membranes for all vanadium redox flow batteries

Polyvinylpyrrolidone-based semi-interpenetrating polymer networks (SIPNs) are fabricated for vanadium redox flow batteries. The PVP-based SIPNs exhibit extremely low vanadium permeabilities, which is attributed, in part, to the small well-established ionic clusters, and in part, to the fact that there exists Donnan exclusion effect between the vanadium ions and protonated pyrrolidone groups as a result of a protonation process among pyrrolidone groups and the doped acid. Hence, the coulombic efficiency of VRFBs with the PVP-based SIPNs reaches almost 100% at the current densities ranging from 40 mA cm−2 to 100 mA cm−2.317