Electrochemical Impedance Spectroscopic Investigation of Vanadium Redox Flow Battery

• Published in: Journal of the Electrochemical Society 2022-05, Vol.169 (5), p.50513
• Main Authors: Tripathi, Anand Kumar, Choudhury, Debittree, Joy, Miji E, Neergat, Manoj
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/ac6aeb

The kinetics of redox reactions relevant to vanadium redox flow battery (VRFB) is investigated using voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a three-electrode configuration and in a VRFB setup (two-electrode configuration). Impedance spectra are recorded in the VRFB setup with equimolar concentration of V 5+ /V 4+ and V 3+ /V 2+ solutions as positive and negative electrolytes, respectively (full-cell; asymmetric feed system); with an equimolar V 5+ /V 4+ electrolyte on both sides (symmetric feed system 1); and also with V 3+ /V 2+ electrolyte on both sides (symmetric feed system 2). Impedance of the full-cell VRFB (recorded with asymmetric feed system) is comparable to the sum of the half of the impedance of symmetric feed systems (of V 5+ /V 4+ and V 3+ /V 2+ electrolytes) at open circuit potential (OCP). Impedance and voltammograms recorded in the three-electrode configuration using Vulcan XC-72 modified rotating disk electrode, and the impedance recorded in the two-electrode full-cell configuration unequivocally confirms that the V 5+ /V 4+ redox reaction limits the VRFB performance. The optimal performance of the VRFB with the in situ treated carbon felt compressed to 47% is ∼389 and ∼336 mW cm −2 with 5 and 25 cm 2 cell area, respectively.