Effect of PEM Equivalent Weights and Carbon Electrodes 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. Towards that end, we have explored a series of experimental PEM-based materials and carbon electrodes. We present a detailed analysis of 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. The results are compared directly to commercially available Nafion 212® and suggest markedly improved performance and power densities in excess of 500 mW/cm².