Low-Cost Pore-Filled PVDF–Nafion Composite Membrane for the Vanadium Redox Flow Battery

Nafion solution is used as the filler for the porous polyvinylidene fluoride (PVDF) membrane for reducing the crossover of vanadium species in the vanadium redox flow battery (VRFB). Scanning electron microscopy confirmed the uniform penetration of the Nafion solution throughout the membrane. Water uptake, Nafion consumption, and permeability of vanadium ions of the PVDF–Nafion membrane are significantly smaller than those of the Nafion117 membrane. Vanadium permeability of the PVDF–Nafion composite membrane is 18 times lower than that of the Nafion117 membrane. Furthermore, owing to the reduction in vanadium permeability, the PVDF–Nafion membrane retains 70% more capacity than the Nafion117 membrane. PVDF–Nafion-5% shows stable voltage efficiency, demonstrating the robustness of the synthesized membrane. On the flip side, the composite membrane shows reduced proton conductivity. Therefore, in this paper, a strategy is shown of how to tackle the additional overpotential due to reduced proton conductivity. Further, the economic advantage and feasibility is justified using techno-economic assessment for the 1 kW–1 kW·h VRFB system assembled with the PVDF–Nafion composite membrane. The results show that the developed PVDF–Nafion membrane is a good alternative to the Nafion117 membrane in the VRFB due to its low cost, low vanadium permeability, and better cyclability up to 800 charge–discharge cycles.