Advanced poly(vinyl pyrrolidone) decorated chlorinated polyvinyl chloride membrane with low area resistance for vanadium flow battery

A novel chlorinated polyvinyl chloride (CPVC) membrane with low area resistance and excellent cycling performance was prepared for vanadium flow batteries (VFBs). Poly(vinyl pyrrolidone) (PVP), in which amine groups could be protonated in the acidic conditions, was introduced into CPVC membrane to conduct ions. The positively charged protonated amine groups can not only form successive and smooth pathways for ion transport, but also prevent the cross contamination of vanadium electrolytes based on Donnan exclusion. Besides, the protonated amine groups, which continually and intensively distribute on the surface along with domains near the surface, are considerably beneficial to rapid and free transport of protons, thereby lowering area resistance. Consequently, the VFB based on the resultant CPVC/PVP membrane demonstrated excellent performance with a voltage efficiency of around 80% at 200 mA cm−2 (higher than that of commercial Nafion 115), which enabled higher power density of VFBs. Furthermore, this battery continuously ran for over 300 cycles at 80 mA cm−2, indicating great chemical stability of the CPVC/PVP membrane. The application of such high-performance CPVC/PVP membrane extends the choice of membrane materials and could be of high significance for the further development of VFBs.