Flow battery cleansing cycle to maintain electrolyte health and system performance

Patent metadata

Field	Value
Publication number	US-2018316037-A1
Application number	US-201815965722-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 cleansing a redox flow battery system may include operating the redox flow battery system in a charge, discharge, or idle mode, and responsive to a redox flow battery capacity being less than a threshold battery capacity, mixing the positive electrolyte with the negative electrolyte. In this way, battery capacity degradation following cyclic charging and discharging of the redox flow battery system can be substantially reduced.

First claim

1 . A method of operating a redox flow battery system, including:
circulating a positive electrolyte between a positive electrode compartment and a positive electrolyte chamber with a positive electrolyte pump, circulating a negative electrolyte between a negative electrode compartment and a negative electrolyte chamber with a negative electrolyte pump, and responsive to a first condition, including when a redox flow battery capacity is less than a threshold battery capacity, performing a battery cleansing cycle, including mixing the positive electrolyte with the negative electrolyte until a redox flow battery state of charge (SOC) is less than a threshold SOC.

2 . The method of claim 1 , wherein the first condition further includes when a SOC of the positive electrolyte is less than a threshold discharge SOC.

3 . The method of claim 2 , wherein the first condition further includes when a pH of the positive electrolyte is less than a threshold pH.

4 . The method of claim 1 , wherein mixing the positive electrolyte with the negative electrolyte includes opening a first mixing valve to direct flow of the positive electrolyte from the positive electrolyte chamber to the negative electrolyte chamber.

5 . The method of claim 4 , wherein mixing the positive electrolyte with the negative electrolyte includes activating the negative electrolyte pump while opening the first mixing valve.

6 . The method of claim 5 , wherein mixing the positive electrolyte with the negative electrolyte includes deactivating the positive electrolyte pump while opening the first mixing valve.

7 . The method of claim 6 , wherein mixing the positive electrolyte with the negative electrolyte includes opening the first mixing valve for a first threshold duration.

8 . The method of claim 2 , wherein performing the battery cleansing cycle includes switching operation of the redox flow battery system to a discharge mode when a SOC of the positive electrolyte is greater than the threshold discharge SOC.

9 . The method of claim 3 , wherein performing the battery cleansing cycle includes directing flow of the positive electrolyte through a rebalancing reactor when a pH of the positive electrolyte is greater than the threshold pH.

10 . The method of claim 7 , further comprising, responsive to the first threshold duration elapsing, closing the first mixing valve and opening a second mixing valve to direct electrolyte from the negative electrolyte chamber to the positive electrolyte chamber.

11 . A method of cleansing a redox flow battery system, including:
operating the redox flow battery system in a charge, discharge, or idle mode, and responsive to a redox flow battery capacity being less than a threshold battery capacity,
switching the redox flow battery system to operate in the discharge mode, and
reducing electrolyte state of charge (SOC) by directing positive and negative electrolytes to flow through rebalancing reactors.

12 . The method of claim 11 , further comprising, responsive to a SOC and a pH of the positive electrolyte being less than a threshold positive electrolyte SOC and a threshold pH, respectively, mixing the positive electrolyte with the negative electrolyte.

13 . The method of claim 12 , wherein mixing the positive electrolyte with the negative electrolyte includes flowing electrolytes from a positive electrode compartment to a negative electrode compartment for a first threshold duration.

14 . The method of claim 13 , further comprising, after the first threshold duration elapses, flowing electrolytes from the negative electrode compartment to the positive electrode compartment for a second threshold duration.

15 . The method of claim 14 , further comprising fluidly isolating the negative electrode compartment and the positive electrode compartment for a time delay following the first threshold duration and prior to the second threshold duration.

16 . The method of claim 15 , wherein the first threshold duration increases with a difference between the redox flow battery capacity and the threshold battery capacity.

17 . A redox flow battery system, including:
a redox flow battery cell with a positive electrode compartment and a negative electrode compartment; a mixing valve fluidly coupled between the positive electrode compartment and the negative electrode compartment; positive and negative electrolyte pumps for circulating electrolyte through the positive electrode compartment, and a controller, including executable instructions stored in memory thereon to, responsive to a redox flow battery capacity being less than a threshold battery capacity, perform a battery cleansing cycle, including mixing the positive electrolyte with the negative electrolyte.

18 . The redox flow battery system of claim 17 , wherein the executable instructions to mix the positive electrolyte with the negative electrolyte include opening the mixing valve for a first threshold duration while activating the negative electrolyte pump and deactivating the positive electrolyte pump.

19 . The redox flow battery system of claim 18 , wherein the executable instructions further include, after the first threshold duration, closing the mixing valve while deactivating the negative electrolyte pump and activating the positive electrolyte pump.

20 . The redox flow battery system of claim 19 , wherein the executable instructions further include stopping the battery cleansing cycle when a redox flow battery state of charge (SOC) is less than a threshold SOC.

Assignees

• Ess Technology Inc

Inventors

• Song Yang
• Evans Craig E

Classifications

• H01M8/0693

  Treatment of the electrolyte residue, e.g. reconcentrating · CPC title

• H01M8/04611

  of the individual fuel cell · CPC title

• H01M8/188 Primary

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

• H01M8/04932

  of the individual fuel cell · CPC title

• H01M8/04186

  of liquid-charged or electrolyte-charged reactants · CPC title