Application of in situ bismuth deposition towards performance enhancements in high-power operation of industrial scale vanadium redox flow batteries

Operating a vanadium redox flow battery (VRFB) at high powers leads to a significant reduction of the extractable/storable energy. In the present work, we report on studies of catalytic activation of industrial-scale VRFB cells using in situ deposition of Bismuth (Bi) on in-house thermally activated electrodes to achieve high-power operation. The presence of Bi on the electrode is confirmed by scanning electron microscopy and inductively coupled plasma analyses. The effect of HCl addition to the sulfuric acid-based electrolyte is systematically studied through cyclic voltammetry. These basic studies have been supplemented by polarization and charge-discharge cycling (CDC) tests on a 936 cm 2 VRFB cell in the current density range of 120–240 mA.cm −2 and in the Bi concentration range of 0.01–0.03 M. Comparative studies have also been conducted with untreated and thermally activated electrodes to bring out the differential effect of catalytic activation at cell level performance. These studies show that around 20 % improvement in the energy storage capacity can be achieved through catalytic activation of the electrode compared to the thermally activated electrode at an operating current density of 150 mA.cm −2 . • Large cell study of effectiveness of bismuth-based catalytic activation. • Synchronous deposition of Bi catalyst particles on electrode. • VRFB cell testing in the current density range of 120–240 mA.cm −2 . • Deconvolution of mixed acid and Bi catalytic activation on cell performance. • Over 18 % improvement in energy density at 150 mA.cm −2 .