MITIGATION OF SOLUTION CROSS-OVER USING DIFFERENTIAL ELECTROLYTE FORMULATIONS IN REDOX FLOW BATTERY SYSTEMS

Abstract

A redox flow battery system having decreased cross-over of active species and decreased hydrogen generation, which is particularly important with less expensive polyethylene or polypropylene membranes. The redox flow battery system comprises at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte. The positive electrolyte is in contact with a positive electrode, and the negative electrolyte is in contact with a negative electrode. The positive and negative electrolytes comprise water and a metal precursor, and the concentration of the metal precursor in the negative electrolyte is greater than the concentration of the metal precursor in the positive electrolyte. The metal in the metal precursor comprises iron, copper, zinc manganese, titanium, tin, silver, vanadium, or cerium.

Claims

1. A redox flow battery system, comprising: at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; and wherein the metal in the metal precursor comprises iron, copper, zinc manganese, titanium, tin, silver, vanadium, or cerium.

2. The battery system of claim 1 wherein the metal comprises iron or copper.

3. The battery system of claim 1 wherein the metal comprises iron and wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof.

4. The battery system of claim 1 wherein: the metal precursor in the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; and the metal precursor in the positive electrolyte comprises FeCl.sub.2, at the concentration of 0.5-4.0 M.

5. The battery system of claim 1 wherein the separator comprises an ionically conductive membrane.

6. The battery system of claim 5 wherein the ionically conductive membrane comprises an ionically conductive thin film composite membrane, an ionically conductive asymmetric composite membrane, a size exclusion membrane, an anion exchange membrane, or a cation exchange membrane.

7. The battery system of claim 1 wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of: an amino acid, an inorganic acid, an organic acid, a supporting electrolyte, and boric acid.

8. The battery system of claim 7 wherein at least one of: the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof.

9. The battery system of claim 1 wherein: the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid; optionally glycine; and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3.

10. The battery system of claim 1 wherein a volume of the negative electrolyte is less than a volume of the positive electrolyte.

11. A redox flow battery system, comprising: at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; wherein the metal in the metal precursor comprises iron; and wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof.

12. The battery system of claim 11 wherein: the metal precursor in the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; and the metal precursor in the positive electrolyte comprises FeCl.sub.2, at the concentration of 0.5-4.0 M.

13. The battery system of claim 11 wherein the separator is an ionically conductive membrane comprising an ionically conductive thin film composite membrane, an ionically conductive asymmetric composite membrane, a size exclusion membrane, an anion exchange membrane, or a cation exchange membrane.

14. The battery system of claim 11 wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of: an amino acid, an inorganic acid, a supporting electrolyte, and boric acid.

15. The battery system of claim 14 wherein at least one of: the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof.

16. The battery system of claim 11 wherein: the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid; optionally glycine; and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3.

17. The battery system of claim 11 wherein a volume of the negative electrolyte is less than a volume of the positive electrolyte.

18. A redox flow battery system, comprising: at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; wherein the metal in the metal precursor comprises iron; wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof; and wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of: an amino acid, an inorganic acid, a supporting electrolyte, and boric acid.

19. The battery system of claim 18 wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of: an amino acid, an inorganic acid, a supporting electrolyte, and boric acid; and wherein at least one of: the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof.

20. The battery system of claim 18 wherein: the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid; optionally glycine; and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3.

Description

EXAMPLES

Example 1

Anolyte Formulation Procedure

[0062] The negative electrolyte solution comprised 2.5M FeCl.sub.2, 3.0M NH.sub.4Cl, and 0.2M glycine. It was prepared by dissolving FeCl.sub.2.4H.sub.2O in deaerated 18.2 MΩcm, followed by the addition of NH.sub.4Cl. Glycine was then added. All steps were performed under constant N.sub.2 purge. The pH was adjusted to about 1.5 using HCl. The volume was adjusted to achieve the desired concentrations.

Catholyte Formulation Procedure

[0063] The positive electrolyte solution comprised 1.5M FeCl.sub.2, 3.0M NH.sub.4Cl, and 0.2M glycine. It was prepared by dissolving FeCl.sub.2.4H.sub.2O in deaerated 18.2 MΩcm, followed by the addition of NH.sub.4Cl and then glycine. All steps were performed under constant N.sub.2 purge. The pH was adjusted to about 1.5 using HCl. The volume was adjusted to achieve the desired concentrations.

Solution Cross-Over Testing

[0064] 120 ml of anolyte and 200 ml of catholyte were loaded into a 25 cm.sup.2 IFB, and the battery was cycled at 12 mA/cm.sup.2 for 21 h. The test was conducted at room temperature using a porous membrane known to allow for water crossover.

[0065] This battery showed no solution movement after 21 h of charging, while another battery which had 1.5M FeCl.sub.2 on both sides showed about 10% volume movement toward the catholyte at end of ˜21 h of charging.

Example 2

Anolyte Formulation Procedure

[0066] The negative electrolyte solution comprised 1.25 M FeCl.sub.2, 2.0M NaCl, and 0.2M boric acid. It was prepared by dissolving FeCl.sub.2.4H.sub.2O in deaerated 18.2 MΩcm, followed by the addition NaCl, Then, boric was added. All steps were performed under constant N.sub.2 purge. The pH was adjusted to about 1.5 using HCl. The volume was adjusted to achieve the desired concentrations.

Catholyte Formulation Procedure

[0067] The positive electrolyte solution comprised 0.75 M FeCl.sub.2, 2.0 M NaCl, and 0.2M boric. It was prepared by dissolving FeCl.sub.2.4H.sub.2O in deaerated 18.2 MΩcm, followed by the addition NaCl. Boric was then added. All steps were performed under constant N.sub.2 purge. The pH was adjusted to about 1.5 using HCl. The volume was adjusted to achieve the desired concentrations.

Solution Cross-Over Testing

[0068] 120 ml of anolyte and 100 ml of catholyte were loaded into a 25 cm.sup.2 IFB, and the battery was cycled with 2 h charge and discharge at 30 mA/cm.sup.2. The test was conducted at room temperature using a porous membrane known to allow for water crossover.

SPECIFIC EMBODIMENTS

[0069] While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

[0070] A first embodiment of the invention is a system, comprising at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; and wherein the metal in the metal precursor comprises iron, copper, zinc manganese, titanium, tin, silver, vanadium, or cerium. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal comprises iron or copper. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal comprises iron and wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof; An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal precursor in the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; and the metal precursor in the positive electrolyte comprises FeCl.sub.2, at the concentration of 0.5-4.0 M. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the separator comprises an ionically conductive membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the ionically conductive membrane comprises an ionically conductive thin film composite membrane, an ionically conductive asymmetric composite membrane, a size exclusion membrane, an anion exchange membrane, or a cation exchange membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of an amino acid, an inorganic acid, an organic acid, a supporting electrolyte, and boric acid. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein at least one of the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid; optionally glycine; and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a volume of the negative electrolyte is less than a volume of the positive electrolyte.

[0071] A second embodiment of the invention is a redox flow battery system, comprising at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; wherein the metal in the metal precursor comprises iron; and wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the metal precursor in the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; and the metal precursor in the positive electrolyte comprises FeCl.sub.2, at the concentration of 0.5-4.0 M. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the separator is an ionically conductive membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the ionically conductive membrane is an ionically conductive thin film composite membrane, an ionically conductive asymmetric composite membrane, a size exclusion membrane, an anion exchange membrane, or a cation exchange membrane. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of an amino acid, an inorganic acid, a supporting electrolyte, and boric acid. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein at least one of the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid, optionally glycine, and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein a volume of the negative electrolyte is less than a volume of the positive electrolyte.

[0072] A third embodiment of the invention is a redox flow battery system, comprising at least one rechargeable cell comprising a positive electrolyte, a negative electrolyte, and a separator positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte in contact with a positive electrode, and the negative electrolyte in contact with a negative electrode; the positive electrolyte comprising water and a metal precursor; and the negative electrolyte comprising water and the metal precursor; wherein a concentration of the metal precursor in the negative electrolyte is greater than a concentration of the metal precursor in the positive electrolyte; wherein the metal in the metal precursor comprises iron; wherein the metal precursor comprises FeCl.sub.2, FeCl.sub.3, FeSO.sub.4, Fe.sub.2(SO.sub.4).sub.3, FeO, Fe, Fe.sub.2O.sub.3, or combinations thereof; and wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of an amino acid, an inorganic acid, a supporting electrolyte, and boric acid. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the positive electrolyte, the negative electrolyte, or both further comprise at least one of an amino acid, an inorganic acid, a supporting electrolyte, and boric acid; and wherein at least one of the amino acid comprises an amino acid having a side chain length of 1 to 6 carbon atoms; the inorganic acid comprises HCl, H.sub.2SO.sub.4, or combinations thereof; and the supporting electrolyte comprises an ion comprising Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Ba.sup.2+, Mg.sup.2+, SO.sub.4.sup.2−, F.sup.−, Cl.sup.−, or combinations thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the negative electrolyte comprises FeCl.sub.2 at the concentration of 1.0-4.5 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally boric acid; optionally glycine; and optionally FeCl.sub.3; and the positive electrolyte comprises FeCl.sub.2 at the concentration of 0.5-4.0 M; NaCl, KCl, NH.sub.4Cl, or combinations thereof; optionally HCl; optionally glycine; optionally boric acid; and optionally FeCl.sub.3.

[0073] Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0074] In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.