Near to neutral pH all-iron redox flow battery based on environmentally compatible coordination compounds

• A pH 8.6 redox flow battery using nontoxic iron-coordination compounds is presented. The cell shows a voltage of 848 mV at 50% SOC and capacity retention nearly 100%. peak power density 44.5 mW cm –2 was achieved 95 mA current density. Reactant crossover N-324 SPEEK membranes 5·10 –12 2 s –1 6.2·10 –11 . system promising option as environmentally friendly electrolytes. We demonstrate near to neutral carriers in both negative positive electrolyte contains compound commercially use fertilizer, the racemic form iron(III)-N,N’-ethylene-bis-(o-hydroxyphenylglycine), with reduction potential -613 vs Ag/AgCl, 1 M NaCl. sodium ferrocyanide, +235 3 KCl. all-iron aqueous exhibits state-of-charge (SOC). solubility for reactants this work up ∼0.2 M. Permeation experiments were performed three different cation exchange membranes: Nafion NR-212 N-324, low-cost sulfonated poly(ether ketone) membranes. 100% over 75 charge discharge cycles membrane. No significant decay or efficiency observed during two days cycling low 14% high 93% SoC limits. Using (SPEEK) membrane, good utilization 86.5% demonstrated 81.5% 25 density, However, detected. , respectively. new combination iron complexes represents stationary energy storage applications.