High solubility iron hexacyanides

Patent metadata

Field	Value
Publication number	US-2019363388-A1
Application number	US-201916533475-A
Country	US
Kind code	A1
Filing date	Aug 6, 2019
Priority date	Aug 15, 2012
Publication date	Nov 28, 2019
Grant date	—

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:

1 . An alkaline aqueous solution, comprising:
(a) an iron hexacyanide complex; and (b) at least two different alkali metal counterions; the concentration of said iron hexacyanide complex, at a given temperature, being higher than can be obtained when said iron hexacyanide complex is in the presence of any single one of the at least two different alkali metal counterions; and wherein the alkaline aqueous solution is substantially free of alkaline earth metal cations.

2 . The solution of claim 1 , wherein the solution is stable to precipitation at a temperature in the range of from about −10° C. to about 60° C.

3 . The solution of claim 1 , wherein the at least two different alkali metal counterions include Na + and K + .

4 . The solution of claim 1 , wherein two of the at least two different alkali metal counterions are present at a molar ratio in the range of from about 1:10 to about 10:1, with respect to one another.

5 . The solution of claim 4 , wherein the different alkali metal cations are Na + and K + cations, present in a ratio of Na + :K + in the range of from about 1:5 to about 5:1.

6 . The solution of claim 1 , wherein the solution has a pH in a range of from 9 to 14.

7 . The solution of claim 1 , wherein the concentration of the iron hexacyanide complex is at least about 1.1 M,

8 . The solution of claim 1 , wherein the concentration of the iron hexacyanide complex is at least about 1.2 M.

9 . The solution of claim 1 , further comprising a viscosity modifier or a wetting agent.

10 . The solution of claim 1 , further comprising a buffering agent and/or a supporting electrolyte.

11 . The solution of claim 1 , further comprising another species which is redox active over a range of from about −0.8 V to about 1.8 V, vs. RHE.

12 . The solution of claim 1 consisting essentially of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 20 A-h/L.

13 . The solution of claim 12 consisting essentially of an alkaline solution of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 30 A-h/L.

14 . An electrochemical cell having at least one half-cell comprising a solution of claim 1 .

15 . The electrochemical cell of claim 14 , wherein the at least one half-cell comprises a solution of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 20 A-h/L.

16 . The electrochemical cell of claim 14 , wherein the at least one half-cell consists essentially of an alkaline solution of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 20 A-h/L.

17 . The electrochemical cell of claim 14 , wherein the at least one half-cell comprises a solution of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 30 A-h/L.

18 . The electrochemical cell of claim 14 , wherein the at least one half-cell consists essentially of an alkaline solution of iron(II) hexacyanide, iron(III) hexacyanide, or a mixture of iron(II) hexacyanide and iron(III) hexacyanide capable of exhibiting a theoretical charge/discharge density of at least about 30 A-h/L.

19 . The electrochemical cell of claim 14 , wherein the cell is a flow battery cell.

20 . An energy storage system comprising a series array of electrochemical cells, wherein at least one electrochemical cell is an electrochemical cell of claim 14 .

Assignees

• Lockheed Martin Advanced Energy Storage Llc

Inventors

• Esswein Arthur J
• Goeltz John
• Amadeo Desiree

Classifications

• H01M8/20

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

• H01M8/222 Primary

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

• H01M8/08

  Fuel cells with aqueous electrolytes · CPC title

• H01M8/188 Primary

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

• C01C3/12 Primary

  Simple or complex iron cyanides · CPC title