Alkaline Redox Flow Batteries

Abstract

Redox flow batteries (RFBs) are rapidly emerging as the“one of the most practical solution for grid-scale energy storage and energy management due to their relative simplicity, high performance, long lifetimes and decoupled power and capacity. In addition, the use of redox active organic molecules”to store energy have several advantages than other conventional redox flow battery (e.g., vanadium-based) such as higher energy efficiency, solubility, multiple number of electron transfer and rapid electron transfer kinetics. In this work, we reported the organic electrolyte based alkaline redox flow battery using“reactants composed of only earth-abundant”material which are nonflammable, not expansive, non-toxic and working in alkaline medium (pH = 14). Alloxazine ester, inspired from vitamin B12 structure, was used at the negative side of the RFB and ferrocyanide or manganate were used at the positive side. The use of manganate at the positive side was investigated at concentration up to 100 mM and limited by manganese oxide platting on the battery components (electrodes and membrane). As a consequence, ferrocyanide was used as posolyte for battery cycling at higher concentration (0.4 M ferrocyanide at the positive side and 0.38 M alloxazine ester at the negative side). Finally, the alkaline RFB reached high performances up to 100 cycles with the volumetric capacity of 17.41 Ah L-1 including 98 % coulombic efficiency per cycle and“average voltage and energy efficiencies”of 91 % and 90%, respectively.