# US 2021/0242479 A1 · Electrolyte health management for redox flow battery

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- Number: US 2021/0242479 A1
- Document ID: US20210242479A1
- Status: Published application
- Kind: A1
- Application number: 17/234,509
- Filed: 2021-04-19
- Published: 2021-08-05
- Earliest claimed: 2018-11-20
- Assignees: Ess Tech, Inc.
- Applicants: Ess Tech, Inc.
- Inventors: Yang Song; Timothy J. McDonald; Alexandria Behr
- Web page: https://patentgrep.com/patent/US20210242479A1

## CPC

- H01M 8/0693: {Treatment of the electrolyte residue, e.g. reconcentrating}
- H01M 8/04186: of liquid-charged or electrolyte-charged reactants
- H01M 8/04201: {Reactant storage and supply, e.g. means for feeding, pipes}
- H01M 8/0444: Concentration; Density (H01M8/04492 takes precedence)
- H01M 8/04477: {of the electrolyte}
- H01M 8/04753: {of fuel cell reactants}
- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01M 2300/0005: Acid electrolytes
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Methods and systems are provided for a rebalancing reactor of a flow battery system. In one example, a pH of a battery electrolyte may be maintained by the rebalancing reactor by applying a negative potential to a catalyst bed of the rebalancing reactor. A performance of the rebalancing reactor may further be maintained by treating the catalyst bed with deionized water.

## Claims

### Claim at position 1

1-8. (canceled)

### Claim 9

A redox flow battery system, comprising;
an electrolyte circulating through a cell of the redox flow battery and hydrogen gas stored in electrolyte chambers of the redox flow battery, both the electrolyte and hydrogen gas flowed to a rebalancing reactor coupled to the cell;
a negative potential applied to the catalyst bed during charging of the redox flow battery;
a controller, configured with computer readable instructions stored on non-transitory memory, the instructions executable by the controller to:
apply a negative potential to the catalyst bed during charging of the redox flow battery;
flush the catalyst bed with deionized water upon detection of the rate of ferric iron reduction at the rebalancing reactor falling below a second threshold; and
indicate a request for soaking of the catalyst bed in deionized water when an interval of operating time of the redox flow battery is elapsed.

### Claim 10 (depends on 9)

The redox flow battery system claim 9, wherein the electrolyte includes ferric and ferrous iron complexes, non-redox active salts, and an acid.

### Claim 11 (depends on 9)

The redox flow battery system of claim 9, where the hydrogen gas is generated at a negative electrode of the cell in a process that consumes protons from the electrolyte.

### Claim 12 (depends on 9)

The redox flow battery system of claim 9, wherein the catalyst bed of the rebalancing reactor has a jelly roll structure.

### Claim 13 (depends on 9)

The redox flow battery system of claim 9, wherein the negative potential applied to the catalyst bed is configured to generate a negative charge at the catalyst bed and wherein the negative potential is applied continuously during operation of the redox flow battery.

### Claim 14 (depends on 9)

The redox flow battery system of claim 9, wherein the catalyst bed is flushed with deionized water while housed in the rebalancing reactor when deionized water is flowed through the rebalancing reactor.

### Claim 15 (depends on 9)

The redox flow battery system of claim 9, wherein the catalyst is soaked when the redox flow battery system is deactivated and the catalyst is removed from the rebalancing reactor.

### Claim at position 9

16-20. (canceled)