Chunxiao Wu

Layer-by-layer self-assembly of Nafion–[CS–PWA] composite membranes with suppressed vanadium ion crossover for vanadium redox flow battery applications

A novel polymer–inorganic composite membrane, Nafion–[CS–PWA]n (n = the number of bilayers), was prepared by a layer-by-layer self-assembly technique with polycation chitosan (CS) and negatively charged phosphotungstic acid (PWA) for vanadium redox flow battery applications. The UV-visible spectra and SEM results showed that the CS–PWA multilayer was successfully fabricated on the surface of the Nafion membrane, and the FTIR result showed that there was a strong interaction between the CS and PWA molecules. The obtained Nafion–[CS–PWA]n showed much lower vanadium ion permeability compared with the pristine Nafion membrane. Accordingly, the VRFB with the Nafion–[CS–PWA]3 membrane exhibited higher coulombic efficiency (CE) and energy efficiency (EE) together with a slower self-discharge rate than that of the pristine Nafion212 system.

A novel polysulfone–polyvinylpyrrolidone membrane with superior proton-to-vanadium ion selectivity for vanadium redox flow batteries

A novel kind of effective vanadium ion-suppressed polysulfone–polyvinylpyrrolidone (PSF–PVP) membrane with high ion selectivity, superior stability and low cost is designed and constructed for vanadium redox flow batteries (VRFBs). The VRFB with the PSF–PVP–50 membrane exhibits impressive coulombic efficiency (98%) as well as energy efficiency (89%), and outstanding stability during the 2000 h continuous charge–discharge cycling test.

A Bunch-Like Tertiary Amine Grafted Polysulfone Membrane for VRFBs with Simultaneously High Proton Conductivity and Low Vanadium Ion Permeability

Novel polysulfone membranes with bunch-like tertiary amine groups are synthesized with high ion selectivity and outstanding chemical stability for vanadium redox flow batteries (VRFBs). The bunch-like tertiary amine groups simultaneously act as an ionic conductor for proton hopping and vanadium ion transport obstacles. The performance of the membrane is tuned via controlling the grafting degree of the chloromethylated polysulfone. The results show that membranes show increasing proton over vanadium ion (σ/p) selectivity with increasing functional tertiary groups. VRFBs assembled with the prepared membranes demonstrate an impressive Coulombic efficiency of 98.9% and energy efficiency of 90.9% at a current density of 50 mA cm-2 . Furthermore, the prepared membrane reported in this work shows excellent stability in 1 m VO2+ solution at 35 °C over 240 h. Overall, the synthesized polymers provide a new insight into the design of high-performance membranes toward VRFB applications.