Methods and systems for operating a redox flow battery system

Patent metadata

Field	Value
Publication number	US-2018316032-A1
Application number	US-201815965709-A
Country	US
Kind code	A1
Filing date	Apr 27, 2018
Priority date	Apr 28, 2017
Publication date	Nov 1, 2018
Grant date	—

Abstract

A method of operating a redox flow battery, may include maintaining a positive electrode compartment pressure greater than a negative electrode compartment pressure, and maintaining a cross-over pressure less than a membrane break-through pressure, wherein the cross-over pressure equals the negative electrode compartment pressure subtracted from the positive electrode compartment pressure. In this way, ionic resistance across the separator can be maintained at a lower level by reducing gas bubbles trapped therein while reducing separator break-through, thereby increasing performance of the redox flow battery system.

First claim

1 . A method of operating a redox flow battery, comprising:
in response to an increase in a resistance of the redox flow battery being greater than a threshold increase in resistance, increasing a cross-over pressure by performing one or more of, increasing a positive electrode compartment pressure of the redox flow battery, and reducing a negative electrode compartment pressure of the redox flow battery, wherein the cross-over pressure equals the negative electrode compartment pressure subtracted from the positive electrode compartment pressure.

2 . The method of claim 1 , further comprising, in response to charging the redox flow battery system, increasing the cross-over pressure to a threshold cross-over pressure by performing one or more of, increasing the positive electrode compartment pressure, and reducing the negative electrode compartment pressure.

3 . The method of claim 2 , wherein the threshold cross-over pressure is less than a break-through pressure of a separator membrane of the redox flow battery.

4 . The method of claim 3 , wherein decreasing the negative electrode compartment pressure includes increasing a speed of a vacuum pump fluidly coupled to the negative electrode compartment.

5 . The method of claim 4 , wherein decreasing the negative electrode compartment pressure includes reducing a speed of an electrolyte pump supplying negative electrolyte to the negative electrode compartment.

6 . The method of claim 5 , wherein decreasing the negative electrode compartment pressure includes throttling a back flow pressure regulating device fluidly coupled to an outlet of the negative electrode compartment to increase an outlet flow of negative electrolyte from the negative electrode compartment.

7 . The method of claim 6 , wherein increasing the positive electrode compartment pressure includes increasing a speed of an electrolyte pump supplying positive electrolyte to the positive electrode compartment.

8 . The method of claim 7 , wherein increasing the positive electrode compartment pressure includes throttling a back flow pressure regulating device fluidly coupled to an outlet of the positive electrode compartment to decrease an outlet flow of positive electrolyte from the positive electrode compartment.

9 . A redox flow battery system, comprising:
negative and positive electrode compartments electrically separated by an ionically-permeable separator; negative and positive electrolyte pumps supplying negative and positive electrolyte to the negative and positive electrode compartments, respectively; and a controller, including executable instructions residing in memory on-board the controller to:
in response to charging the redox flow battery system, increasing a cross-over pressure by performing one or more of,
increasing a positive electrode compartment pressure, and
reducing a negative electrode compartment pressure, wherein
the cross-over pressure equals the negative electrode compartment pressure subtracted from the positive electrode compartment pressure.

10 . The redox flow battery system of claim 9 , wherein the executable instructions to reduce the negative electrode compartment pressure include reducing a speed of the negative electrolyte pump.

11 . The redox flow battery system of claim 10 , further comprising a vacuum pump fluidly coupled to the negative electrode compartment, wherein the executable instructions to reduce the negative electrode compartment pressure include increasing a speed of the vacuum pump.

12 . The redox flow battery system of claim 11 , wherein the executable instructions to increase the positive electrode compartment pressure include increasing a speed of the positive electrolyte pump.

13 . The redox flow battery system of claim 12 , further comprising a back flow pressure regulating device fluidly coupled to an outlet of the positive electrode compartment, wherein the executable instructions to increase the positive electrode compartment pressure include decreasing an outlet flow rate of positive electrolyte from the positive electrode compartment by throttling the back flow pressure regulating device.

14 . The redox flow battery system of claim 13 , wherein the ionically-permeable separator includes a hybrid membrane, the hybrid membrane including a microporous membrane layer facing the negative electrode compartment and an ion-exchange membrane layer facing the positive electrode compartment.

15 . The redox flow battery system of claim 13 , wherein the threshold cross-over pressure is from 3 to 7 kPa.

16 . A method of operating a redox flow battery, including:
maintaining a positive electrode compartment pressure greater than a negative electrode compartment pressure, and maintaining a cross-over pressure less than a membrane break-through pressure, wherein the cross-over pressure equals the negative electrode compartment pressure subtracted from the positive electrode compartment pressure.

17 . The method of claim 16 , further comprising, in response to an increase in a resistance of the redox flow battery being less than a threshold increase, reducing the cross-over pressure while maintaining the cross-over pressure greater than a lower threshold cross-over pressure.

18 . The method of claim 17 , further comprising, in response to the increase in the resistance of the redox flow battery begin greater than the threshold increase, increasing the cross-over pressure while maintaining the cross-over pressure less than the membrane break-through pressure.

19 . The method of claim 18 , wherein the increase in the resistance of the redox flow battery is determined over a threshold duration.

20 . The method of claim 18 , wherein the increase in the resistance of the redox flow battery is determined outside of a charging mode.

Assignees

• Ess Technology Inc

Inventors

• Song Yang
• Doremus Evan
• Groberg Thiago

Classifications

• H01M8/04753

  of fuel cell reactants · CPC title

• H01M8/04201

  Reactant storage and supply, e.g. means for feeding, pipes · CPC title

• H01M8/04783 Primary

  Pressure differences, e.g. between anode and cathode · CPC title

• H01M8/188

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

• H01M8/04641

  of the individual fuel cell · CPC title