Membraneless Micro Redox Flow Battery: From Vanadium to Alkaline Quinone

Abstract

First proof‐of‐concept of a membraneless micro redox flow battery with an automated closed‐loop control, using micro actuators and micro sensors, during charge‐discharge continuous operation in recirculation mode is presented in this work. A maximum value of 60 % State of Charge with commercial Vanadium electrolyte, monitored via online spectrometry, is achieved, with a maximum discharge current density of 60 mA/cm2, and a discharge volumetric capacity of 21.5 Ah/L. Next, cycling tests show a decrease in coulombic efficiency of 0.5 % per cycle, and capacity loss. To overcome some drawbacks encountered with Vanadium, an alkaline quinone electrolyte is used instead in the membraneless micro redox flow battery. Using this new electrolyte, sixty continuous cycles are performed showing a decrease in coulombic efficiency of 0.6 % per cycle, and a capacity loss of only 1.2 % per cycle. The performances obtained outshine previous literature results. The highest energy efficiency obtained for a membraneless micro redox flow battery is presented here with alkaline quinone being 28.9 %. Cycling a membraneless micro redox flow battery is achieved for the first time, suggesting improvement of its performance as a future work so that metrics of conventional redox flow batteries are achieved.