Charge-discharge performance of carbon fiber-based electrodes in single cell and short stack for vanadium redox flow battery

Electrode materials, having a different graphitic character, are investigated by using a zero-gap flow field cell configuration for vanadium redox flow battery applications (VRFBs). Carbon felt (CF) and carbon paper (CP) are used as electrodes for the membrane-electrode assemblies (MEAs) realization. The samples are electrochemically characterized both as-received and after chemical treatment by using a 5 cm2 single cell. A Nafion 117 membrane is used as polymer electrolyte separators. A MEAs scale-up from 5 to 25 cm2 is carried out in order to assembly a 3-cells short stack in series connected. Charge-discharge cycles are carried out both in a small area single cell and in a 3-cells short stack for all samples. CF treated and untreated samples show SOC values of 45% vs. 22% at 60 mA cm−2, respectively. After the chemical treatment, the worst performance of the CF sample is attributed to the mass transport issues due to the beginning of corrosion phenomena. On the contrary, CP treated electrode shows a better energy efficiency values than raw sample (72% vs. 67% at 60 mA cm−2) without any morphology change on the electrode surface. A proper stack assembly and flow field scale-up record similar performance to the small single cell configuration.