Aqueous redox flow batteries featuring improved cell design characteristics
This invention is directed to aqueous redox flow batteries comprising ionically charged redox active materials at least one of which is a sulfonated catechol.
1. A flow battery comprising:
a first half-cell containing a first electrolyte solution, the first electrolyte solution comprising a coordination complex as a first active material;
wherein the coordination complex comprises at least one sulfonated catechol as a ligand; and
a second half-cell containing a second electrolyte solution, the second electrolyte solution comprising a form of the sulfonated catechol that is free of metal coordination.
2. The flow battery of claim 1 , wherein the coordination complex comprises a transition metal.
3. The flow battery of claim 1 , wherein the coordination complex comprises a non-zero valence salt of Co, Cr, Sr, Cu, Fe, Mn, Mo, Ni, Pd, Pt, Ru, Sn, Ti, Zr, or V.
4. The flow battery of claim 1 , wherein the coordination complex comprises titanium.
5. The flow battery of claim 1 , wherein the coordination complex comprises a composition of:
M(L 1 )(L 2 )(L 3 ) m
wherein:
L 1 is a sulfonated catecholate, and
L 2 and L 3 are each independently an optionally substituted catecholate, ascorbate, citrate, glycolate, a polyol, gluconate, glycinate, hydroxyalkanoate, malate, maleate, phthalate, sarcosinate, salicylate, or lactate; and
M is a non-zero valent metal or metalloid of Groups 2-16;
m is 0, 1, 2, 3, 4,or 5.
6. The flow battery of claim 1 , wherein the sulfonated catechol is a monosulfonated catechol.
7. The flow battery of claim 1 , wherein the coordination complex further comprises an unsubstituted catecholate ligand or a hydroxycatecholate ligand.
8. The flow battery of claim 1 , wherein the coordination complex further comprises two unsubstituted catecholate ligands.
9. The flow battery of claim 1 , wherein the coordination complex further comprises both Na + and K + counterions.
10. The flow battery of claim 1 , wherein the first half-cell and the second half-cell are separated by a polymer membrane separator.
11. The flow battery of claim 10 , wherein the polymer membrane separator comprises an ionomer.
12. The flow battery of claim 10 , wherein the polymer membrane separator comprises a cationic exchange membrane.
13. A method of operating the flow battery of claim 1 , the method comprising:
alternately reducing an oxidized form of the coordination complex in the first electrolyte solution to a reduced form while oxidizing the sulfonated catechol in the second electrolyte solution to a corresponding sulfonated quinone and then oxidizing the reduced form of the coordination complex in the first electrolyte solution to the oxidized form while reducing the corresponding sulfonated quinone in the second electrolyte solution to form the sulfonated catechol.