In Situ Localized Current Distribution Measurements in All-Vanadium Redox Flow Batteries

A printed circuit board (PCB) was implemented for in-plane, two-dimensional distributed current measurements in an all-vanadium redox flow battery (VRFB). A PCB with built-in shunt resistors is a passive method of measuring localized currents in-situ, in real time. It is demonstrated that lateral current spread through non- or partially-segmented flow field plates will produce a distribution that does not properly reflect the distribution within the electrode; this issue is resolved in this work via fully-segmented flow plates. Large current gradients develop when a cell reaches a mass-transport limitation. Based upon the resultant distributions, it is shown that they reflect a combination of electrolyte velocity and local concentration within the electrode. The impact of flow rate and electrode material properties such as wettability, surface area, porosity, and thickness on current distribution are presented.