Effect of Nanoporous Polysulfone Membranes on the Performance of All-Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRB) are a potentially enabling technology for intermittent, renewable energy sources such as wind and solar power and offer a means for large-scale energy storage. Much of the emphasis of recent research on VRBs has focused on improving the energy density of the device as this will result in significant reductions in the ultimate system cost. Currently one impediment to commercializing VRBs is the cost and stability of the membrane. Towards that end, we have explored a series of experimental nanoporous and acid-functionalized membranes to determine their potential in VRB application, and have observed enhancements over traditional Nafion® and PFSA-based materials. We present a detailed analysis of membrane performance including water and acid uptake and impedance spectroscopy as well as battery performance including charge-discharge cycling to determine the voltage, charge, and energy efficiencies as well as polarization curve analysis that identified losses due to kinetic activation polarization, ohmic polarization due to DC resistance, and mass transport limitations.