Method for iron preformation in redox flow batteries

Patent metadata

Field	Value
Publication number	US-2021135270-A1
Application number	US-202017080702-A
Country	US
Kind code	A1
Filing date	Oct 26, 2020
Priority date	Nov 1, 2019
Publication date	May 6, 2021
Grant date	—

Abstract

Methods and systems are provided for iron preformation in a redox flow battery. In one example, a method may include, in a first condition, discharging and then charging the redox flow battery, and in a second condition, charging the redox flow battery including preforming iron metal at a negative electrode of the redox flow battery, and thereafter entering an idle mode of the redox flow battery including adjusting one or more electrolyte conditions. In some examples, each of preforming the iron metal and adjusting the one or more electrolyte conditions may increase a battery charge capacity to greater than a threshold battery charge capacity.

First claim

1 . A method for a redox flow battery, the method comprising:
in a first condition, discharging the redox flow battery and then charging the redox flow battery without entering an idle mode of the redox flow battery; and in a second condition, charging the redox flow battery, including preforming an iron plating amount at a negative electrode of the redox flow battery, and thereafter entering the idle mode, including adjusting each of an electrolyte pH and an electrolyte state of charge (SOC) imbalance.

2 . The method of claim 1 , further comprising, in a third condition, charging the redox flow battery and then discharging the redox flow battery without entering the idle mode.

3 . The method of claim 2 , further comprising:
determining whether a threshold degradation level of the redox flow battery is met; responsive to the threshold degradation level of the redox flow battery being met, entering the second condition; and responsive to the threshold degradation level of the redox flow battery not being met:
determining an SOC of the redox flow battery,
responsive to the SOC being greater than or equal to a threshold SOC, entering the first condition, and
responsive to the SOC being less than the threshold SOC, entering the third condition.

4 . The method of claim 1 , further comprising, in the second condition:
determining the iron plating amount preformed at the negative electrode during charging of the redox flow battery; and responsive to the iron plating amount being less than a threshold amount, continuing charging the redox flow battery to preform a further iron plating amount.

5 . The method of claim 4 , wherein determining the iron plating amount includes:
determining one or more of a ferric iron electrolyte concentration and a previous cycling efficiency of the redox flow battery; and inferring the iron plating amount based on the one or more of the ferric iron electrolyte concentration and the previous cycling efficiency of the redox flow battery.

6 . The method of claim 1 , wherein, in the second condition:
charging the redox flow battery includes increasing an electrolyte tank pressure to greater than a first threshold pressure; and entering the idle mode includes decreasing the electrolyte tank pressure to less than a second threshold pressure, the second threshold pressure being less than the first threshold pressure.

7 . The method of claim 1 , wherein, in the second condition:
charging the redox flow battery includes increasing a ferric iron electrolyte concentration by a first amount; and entering the idle mode includes decreasing the ferric iron electrolyte concentration by a second amount, the second amount being greater than the first amount.

8 . A redox flow battery system, comprising:
a redox electrode; a plating electrode; an electrolyte subsystem supplying an electrolyte to each of the redox electrode and the plating electrode; one or more sensors; and a controller operable to receive signals from the one or more sensors and storing executable instructions in non-transitory memory, the instructions executable to:
determine one or more system conditioning entry conditions based on the signals received from the one or more sensors; and
responsive to the one or more system conditioning entry conditions being met:
command a charging mode to preform an amount of iron metal at the plating electrode,
command an idle mode to balance one or more conditions of the electrolyte subsystem, and thereafter
further responsive to the amount of iron metal being greater than a threshold amount, enter battery cycling.

9 . The redox flow battery system of claim 8 , wherein the idle mode includes operating the redox flow battery system at less than an idle threshold current.

10 . The redox flow battery system of claim 8 , wherein the charging mode includes supplying a DC current to the redox electrode to charge the redox flow battery system by oxidizing ferric iron at the redox electrode and reducing ferrous iron to plate the amount of iron metal at the plating electrode.

11 . The redox flow battery system of claim 8 , wherein the one or more system conditioning entry conditions comprise the redox flow battery system reaching a threshold degradation level.

12 . The redox flow battery system of claim 11 , wherein determining the one or more system conditioning entry conditions based on the signals received from the one or more sensors includes:
determining a battery charge capacity based on the signals received from the one or more sensors; and responsive to the battery charge capacity being greater than a threshold battery charge capacity, indicating that the redox flow battery system has reached the threshold degradation level.

13 . The redox flow battery system of claim 8 , wherein the one or more conditions of the electrolyte subsystem comprise a ferric iron concentration, a positive electrolyte pH, a negative electrolyte pH, and an electrolyte state of charge imbalance.

14 . The redox flow battery system of claim 13 , wherein the electrolyte subsystem comprises one or more electrolyte balancing reactors, and
wherein balancing the one or more conditions of the electrolyte subsystem includes operating the one or more electrolyte balancing reactors to perform catalytic hydrogen reduction of ferric iron to decrease the ferric iron concentration.

15 . A method, comprising, during system conditioning of a redox flow battery cell:
charging the redox flow battery cell at a set point to increase an electrolyte storage tank pressure; responsive to the electrolyte storage tank pressure being greater than a first threshold pressure, conducting electrolyte rebalancing; and thereafter determining an iron plating amount at a negative electrode of the redox flow battery cell; and responsive to the iron plating amount being less than a threshold amount, continuing charging the redox flow battery cell at the set point.

16 . The method of claim 15 , wherein the threshold amount is selected to increase a battery charge capacity above a threshold battery charge capacity.

17 . The method of claim 15 , wherein the first threshold pressure is selected to prevent rupture or damage of the redox flow battery cell.

18 . The method of claim 15 , wherein conducting electrolyte rebalancing includes:
initiating electrolyte rebalancing to decrease the electrolyte storage tank pressure; and responsive to the electrolyte storage tank pressure being less than a second threshold pressure, ending electrolyte rebalancing, wherein the second threshold pressure is selected to indicate that a threshold amount of hydrogen gas has reacted during electrolyte rebalancing.

19 . The method of claim 18 , wherein initiating electrolyte rebalancing includes:
draining a DC current from the redox flow battery cell to end charging; and operating one or more electrolyte rebalancing reactors.

20 . The method of claim 19 , wherein continuing charging the redox flow battery cell includes reentering charging after ending charging.

Assignees

• Ess Technology Inc

Inventors

• Song Yang
• Thompson Brady
• Mcdonald Timothy J

Classifications

• Y02E60/50

  Fuel cells · CPC title

• Y02B90/10

  Applications of fuel cells in buildings · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M8/04335

  of cathode reactants at the inlet or inside the fuel cell · CPC title

• H01M8/04455

  of cathode reactants at the inlet or inside the fuel cell · CPC title