High solubility iron hexacyanides

Patent metadata

Field	Value
Publication number	US-9742021-B2
Application number	US-201615166174-A
Country	US
Kind code	B2
Filing date	May 26, 2016
Priority date	Aug 15, 2012
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

Stable solutions comprising high concentrations of charged coordination complexes, including iron hexacyanides are described, as are methods of preparing and using same in chemical energy storage systems, including flow battery systems. The use of these compositions allows energy storage densities at levels unavailable by other iron hexacyanide systems.

First claim

What is claimed is the following:

1. A method comprising:
dissolving Na 4 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] in an amount of aqueous solvent to produce an aqueous solution, so as to provide a concentration of Fe(CN) 6 4− in the aqueous solution that exceeds the concentration of Fe(CN) 6 4− in either a saturated aqueous solution of Na 4 [Fe(CN) 6 ] or a saturated aqueous solution of K 4 [Fe(CN) 6 ] in the aqueous solvent at the same temperature;
wherein the aqueous solution is interconvertible between a ferricyanide state and a ferrocyanide state without forming a precipitate in either state.

2. The method of claim 1 , wherein the aqueous solvent has a pH ranging between about 7 and about 14.

3. The method of claim 1 , wherein the aqueous solvent has a pH ranging between about 8 and about 13.

4. The method of claim 1 , wherein Na 4 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] are co-mixed as solids with the aqueous solvent.

5. The method of claim 1 , wherein Na 4 [Fe(CN) 6 ] is added as a solid to a solution of K 4 [Fe(CN) 6 ] in the aqueous solvent.

6. The method of claim 1 , wherein K 4 [Fe(CN) 6 ] is added as a solid to a solution of Na 4 [Fe(CN) 6 ] in the aqueous solvent.

7. The method of claim 1 , wherein the aqueous solvent is substantially free of a co-solvent.

8. The method of claim 1 , wherein the Fe(CN) 6 4− is present in the aqueous solution at a concentration ranging between about 1 M and about 3 M.

9. The method of claim 1 , wherein a molar ratio of sodium ions to potassium ions in the aqueous solution after dissolution of the Na 4 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] ranges between about 1:10 and about 10:1.

10. The method of claim 9 , wherein the molar ratio of sodium ions to potassium ions ranges between about 0.9:1 and about 1.1:1.

11. The method of claim 1 , wherein the aqueous solution contains additional sodium and potassium ions.

Assignees

• Lockheed Martin Advanced Energy Storage Llc

Inventors

• Esswein Arthur J
• Goeltz John
• Amadeo Desiree

Classifications

• H01M8/188 Primary

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• H01M2300/0002

  Aqueous electrolytes · CPC title

• H01M8/222 Primary

  Fuel cells in which the fuel is based on compounds containing nitrogen, e.g. hydrazine, ammonia · CPC title

• H01M8/20

  Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence) · CPC title

• H01M8/08

  Fuel cells with aqueous electrolytes · CPC title