Flow-Platform for Improved Redox Flow Battery Kinetics Measurements

To satisfy continuous energy demand with intermittent renewable energy sources, it is necessary to integrate energy storage technologies into the power grid. Redox flow batteries (RFBs) are promising devices for harnessing electrical energy from renewables like photovoltaics and wind turbines, and distributing it through the power grid. Widespread implementation of current-generation RFBs can be achieved by increasing the battery energy efficiency, which is hindered by slow interfacial electron transfer kinetics between electrolytes and carbon electrodes. However, prior work by our lab and others has shown that common electroanalytical tools such as rotating disk electrodes (RDE) do not adequately decipher electron transfer kinetics at battery relevant electrolyte concentrations.

To address this challenge, we designed a 3-D printed flow platform that employs flat electrode geometries to elucidate electron transfer kinetics under realistic RFB conditions. This analytical system better approximates the hydrodynamic conditions of RFBs, and it is translatable to a variety of electrode/electrolyte combinations, enabling us to test a wide range of materials for RFB advancement. For our purposes, flat carbon electrodes are being developed by subjecting polyacrylonitrile (PAN) to thermal treatments; a process called carbonization. Carbonized PAN is particularly attractive for its chemical resemblance to the non-graphitic carbon fibers used in practical systems. Further, the planar geometry lends to the use of X-ray and microscopy methods for detailed materials characterization that will improve our understanding of electron transfer mechanisms on the carbon surface. We are currently working to integrate our 3D printed platform into a working RFB loop to measure kinetics of RFB electrolytes while the battery is under operation. Thus, this electroanalytical method has great potential to both monitor battery performance in real time and identify electrode/electrolyte pairs with fast kinetics to advance RFBs.