Flow battery with electrolyte rebalancing system

Patent metadata

Field	Value
Publication number	US-2018219241-A1
Application number	US-201815882032-A
Country	US
Kind code	A1
Filing date	Jan 29, 2018
Priority date	Jan 27, 2017
Publication date	Aug 2, 2018
Grant date	—

Abstract

The present invention relates to flow battery systems including a flow battery and an electrolyte rebalancing system. In accordance with certain embodiments, the electrolytes used in the systems of the present invention are aqueous, and in one embodiment, bromine species are used as redox-active species.

First claim

What is claimed is:

1 . A redox flow battery system comprising:
a redox flow battery having a first electrolyte in a first reservoir, the first electrolyte comprising a first redox-active species, a second electrolyte in a second reservoir, the second electrolyte comprising a second redox-active species, and a battery cell having a first compartment in fluid communication with the first reservoir, a second compartment in fluid communication with the second reservoir, an ion permeable membrane separating the first and second compartments, a first electrode in contact with the first compartment, and a second electrode in contact with the second compartment, wherein the first redox-active species is capable of crossing the membrane and contaminating the second electrolyte; and an electrolyte rebalancing system in fluid communication with the second reservoir, wherein the electrolyte rebalancing system is configured to reduce the amount of first redox-active species contaminating the second electrolyte.

2 . The system of claim 1 , wherein the electrolyte rebalancing system comprises a heating unit in fluid communication with the second reservoir and coupled to a condenser, wherein the condenser is in fluid communication with the first reservoir and the second reservoir.

3 . The system of claim 2 , wherein the electrolyte rebalancing system further comprises a heat exchanger, wherein the heat exchanger is in fluid communication with the second reservoir and the heating unit, and the condenser is in fluid communication with the first reservoir and the heat exchanger.

4 . The system of claim 1 , wherein the first redox-active species comprises bromine or bromide.

5 . The system of claim 5 , wherein the heating unit is maintained at below the boiling point of an H 2 O—HBr azeotrope at a given pressure of the heating unit.

6 . The system of claim 5 , wherein the bromine or bromide in the first electrolyte is in a concentration of up to 17 mol %.

7 . The system of claim 6 , wherein the bromine or bromide in the first electrolyte is in a concentration of between about 4 mol % and 8 mol %.

8 . An apparatus comprising:
a first electrolyte reservoir, a second electrolyte reservoir, and a battery cell having a first compartment in fluid communication with the first electrolyte reservoir, a second compartment in fluid communication with the second electrolyte reservoir, a first electrode in contact with the first compartment, and a second electrode in contact with the second compartment; and an electrolyte rebalancing system in fluid communication with the first reservoir and the second reservoir, the electrolyte rebalancing system comprising a heating unit in fluid communication with the second reservoir and coupled to a condenser.

9 . The apparatus of claim 8 , wherein the electrolyte rebalancing system further comprises a heat exchanger, wherein the heat exchanger is in fluid communication with the second reservoir and the heating unit, and the condenser is in fluid communication with the first reservoir and the heat exchanger.

10 . A method of rebalancing electrolyte in a flow battery, the flow battery having a first electrolyte comprising a solvent in a first reservoir, the first electrolyte comprising a first redox-active, wherein the first redox-active-species forms an azeotrope with the solvent; a second electrolyte in a second reservoir, the second electrolyte comprising a second redox-active species; and a battery cell having a first compartment in fluid communication with the first reservoir and a second compartment in fluid communication with the second reservoir, wherein the first compartment and second compartment are separated by an ion permeable membrane, wherein the first redox-active species contaminates the second electrolyte, producing a contaminated electrolyte, the method comprising:
heating the contaminated electrolyte to a temperature below the boiling point of the azeotrope to produce a vapor; condensing the vapor to produce a liquid phase and a vapor phase, wherein the liquid phase comprises a concentration of the first redox-active species greater than the concentration of the first redox-active species in the vapor phase; and directing the liquid phase into the first reservoir or to waste.

11 . The method of claim 10 , further comprising condensing the vapor phase and directing the condensed vapor into the second reservoir.

12 . The method of claim 11 , wherein condensing the vapor comprises passing the vapor through a counter-flow heat exchanger to heat the contaminated electrolyte upstream of the heating unit.

13 . The method of claim 10 , wherein the second redox-active material does not enter the vapor phase in the heating unit and is directed from the heating unit back into the second reservoir.

14 . The method of claim 13 , wherein the second redox-active material is passed through a counter-flow heat exchanger to heat contaminated electrolyte before the second redox-active material is directed back into the second reservoir.

15 . The method of claim 10 , wherein the first redox-active material comprises bromine or bromide.

16 . The method of claim 15 , wherein the first electrolyte has a concentration of up to 17 mol % HBr.

17 . The method of claim 16 , wherein the first electrolyte has a concentration of between about 4 mol % and 8 mol % HBr.

18 . The method of claim 15 , wherein the heating is kept below the boiling point temperature of the H 2 O—HBr azeotrope at a given pressure of the heating unit.

19 . The method of claim 19 , wherein the pressure of the heating is maintained at 1 bar.

20 . The method of claim 19 , wherein the temperature of the heating is maintained between about 100° C. and 126° C.

Assignees

• Harvard College

Inventors

• Chen Qing
• Gordon Roy G
• Aziz Michael J

Classifications

• H01M8/20

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

• H01M8/188 Primary

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

• H01M2300/0005

  Acid electrolytes · CPC title

• H01M8/04276

  Arrangements for managing the electrolyte stream, e.g. heat exchange · CPC title

• H01M8/04007

  related to heat exchange · CPC title