Aqueous redox flow batteries comprising metal ligand coordination compounds

A flow battery comprising:

• a first aqueous electrolyte comprising a first redox active material;
• a second aqueous electrolyte comprising a second redox active material;
• wherein the first and second redox active materials comprise a different metal or metalloid;
• a first electrode in contact with said first aqueous electrolyte;
• a second electrode in contact with said second aqueous electrolyte and
• a separator disposed between said first aqueous electrolyte and said second aqueous electrolyte;
• wherein the first or second redox active material, or both the first and second redox active materials comprise a metal ligand coordination compound having a formula comprising M(L1)x(L2)y(L3)zm, where M is independently a non-zero valent metal or metalloid of Groups 2-16, including lanthanides and actinides,
• wherein x, y, and z are independently 0, 1, 2, or 3, wherein x, y, and z are selected from the group consisting of (a) x=3, y=z=0;
• (b) x=2, y=1, z=0;
• (c) x=1, y=1, z=1;
• m is independently −5, −4, −3, −2, −1, 0, 1, 2, 3, 4, or 5;
• and
• L1, L2, and L3 are each independently ascorbate, citrate, a glycolate, gluconate, glycinate, α-hydroxyalkanoate, β-hydroxyalkanoate, γ-hydroxyalkanoate, malate, maleate, phthalate, a polyol, sarcosinate, salicylate, lactate, or a compound having structure according to Formula I, or an oxidized or reduced form thereof:
• wherein
• Ar is a 5-20 membered aromatic moiety, optionally comprising one of more O, N, or S heteroatoms;
• X1 and X2 are independently —OH, —NHR′, —SH, or an anion thereof, X1 and X2 being positioned ortho to one another;
• R1 is independently at each occurrence H, C1-6 alkoxy, C1-6 alkyl, C1-6 alkenyl, C1-6 alkynyl, 5-6 membered aryl or heteroaryl, a boric acid or a salt thereof, carboxy acid or a salt thereof, C2-6 carboxylate, cyano, halo, hydroxyl, nitro, sulfonate, sulfonic acid or a salt thereof, phosphonate, phosphonic acid or a salt thereof, or a polyglycol;
• R′ is independently H or C1-3 alkyl;
• and
• n is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.