Non-aqueous manganese acetylacetonate electrolyte for redox flow batteries

A single-metal redox flow battery employing manganese(III) acetylacetonate in tetraethylammonium tetrafluoroborate and acetonitrile has been investigated. Cyclic voltammetry was used to evaluate electrode kinetics and reaction thermodynamics. The Mn(II)/Mn(III) and Mn(III)/Mn(IV) redox couples appeared to be quasi-reversible. A cell potential of 1.1 V was measured for the one-electron disproportionation of the neutral Mn(III) complex. The diffusion coefficient for manganese acetylacetonate in the supporting electrolyte solution was estimated to be in the range of 3-5 x 10(-6) cm(2) s(-1) at room temperature. The charge-discharge characteristics of this system were evaluated in an H-type glass cell. Coulombic efficiencies increased with cycling suggesting an irreversible side reaction. Energy efficiencies for this unoptimized system were similar to 21%, likely due to the high cell-component overpotentials. (C) 2011 Elsevier B.V. All rights reserved.