Scaled-up aqueous redox flow battery using anthraquinone negalyte and vanadium posilyte with inorganic additive

In this study, one kilowatt aqueous redox flow battery (ARFB) using anthraquinone-2,7-disulfonic acid (2,7-AQDS) and vanadium oxide sulfate (VOSO₄) as active materials for negalyte (negative electrolyte) and posilyte (positive electrolyte) is successfully accomplished. Then, manganese sulfate (MnSO₄) is further included in negalyte to increase reactivity of active materials and to suppress their crossover by controlling their osmotic pressure. This binary effects of MnSO₄ are predicted by density functional theory and reduction in concentration gap. The decrease in energy band gap of 2,7-AQDS with MnSO₄ facilitated electron transfer rate. Anodic and cathodic diffusion coefficient and reaction rate constant are also improved. More specifically, with adoption of MnSO₄ additive, energy efficiency and capacity retention rate of ARFB single cells operated with MnSO₄ additive are improved from 79.1 to 83.9% at the current density of 40 mA cm⁻² and from 82 to 88% at the current density of 80 mA cm⁻² after 100 cycles. Based on that, ARFB stack using 2,7-AQDS and VOSO₄ with MnSO₄ additive is prepared and this ARFB stack exhibits a high power of 1.15 kW.