One potential next generation battery system is mediated redox flow batteries (RFBs). With mediated RFBs, soluble electroactive species (redox shuttles) deliver power via electrochemical reactions in a flow-through stack reactor much like a conventional RFB. However, the redox shuttles then undergo chemical redox in a coupled chemical reactor system with solid electroactive materials. The use of solid electroactive material for chemical energy storage results in substantial increases in volumetric energy density for the system.

Mediated RFBs with different configurations for the chemical redox reactor have previously been reported. In this work, a packed bed reactor system will be described, where the impact of varying different experimental parameters on the chemical redox progression will be highlighted. Generally, the progression of the chemical redox can be tracked in the lab by taking advantage of electrochemical analytical techniques. However, additional assessment of the reaction progression using neutron imaging will also be discussed. Neutron imaging offered a unique opportunity to access the spatial progression of the chemical redox in the packed bed reactor. The combination of techniques for assessing the chemical redox progression provides insights into the limiting processes in the reactor systems.