# US 11,309,554 B2 · Method and device for recycling electrolyte of flow battery

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,309,554 B2
- Document ID: US11309554B2
- Status: Granted
- Kind: B2
- Application number: 16/345,079
- Filed: 2018-02-09
- Published: 2019-09-12
- Granted: 2022-04-19
- Earliest claimed: 2017-02-10
- Assignees: LG Chem, Ltd.
- Applicants: LG Chem, Ltd.
- Inventors: Geungi Min; Tae Geun Noh; Sikwon Moon; Jeongbae Lee; Bong Hyun Jeong; Sujin Byun; Sungyeon Kim; Joon Ho Park
- Web page: https://patentgrep.com/patent/US11309554B2

## CPC

- H01M 8/04186: of liquid-charged or electrolyte-charged reactants
- H01M 8/04276: Arrangements for managing the electrolyte stream, e.g. heat exchange
- H01M 8/18: Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01M 8/20: Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence)
- H01M 50/77: with external circulating path
- Y02E 60/10: Energy storage using batteries
- 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

The present invention relates to a method for regenerating an electrolyte liquid of a flow battery, and a device for regenerating an electrolyte liquid of a flow battery. The method involves operating a flow battery, stopping the operation of the flow battery, mixing the anode electrolyte liquid and the cathode electrolyte liquid of the flow battery, electrically oxidizing or reducing the mixed electrolyte liquid and dividing the oxidized or reduced electrolyte liquid into each of a cathode electrolyte liquid storage unit and a anode electrolyte liquid storage unit. The device includes a flow battery and a flow battery for regeneration.

## Claims

### Claim 1

A method for regenerating an electrolyte liquid of a flow battery comprising:
providing the flow battery, wherein the flow battery comprises:
an anode,
a cathode,
a separator provided between the anode and the cathode,
an anode electrolyte liquid storage unit that supplies an anode electrolyte liquid to the anode and that stores the anode electrolyte liquid that is discharged from the anode, and
a cathode electrolyte liquid storage unit that supplies a cathode electrolyte liquid to the cathode and that stores the cathode electrolyte liquid that is discharged from the cathode;
charging and discharging of the flow battery repeatedly to generate an unbalanced anode electrolyte liquid and an unbalanced cathode electrolyte liquid;
stopping an operation of the flow battery;
mixing the unbalanced anode electrolyte liquid and the unbalanced cathode electrolyte liquid to produce a mixed electrolyte liquid;
electrically oxidizing or reducing the mixed electrolyte liquid to produce a regenerated electrolyte liquid; and
dividing the regenerated electrolyte liquid into each of the cathode electrolyte liquid storage unit and the anode electrolyte liquid storage unit.

### Claim 2 (depends on 1)

The method for regenerating the electrolyte liquid of the flow battery of claim 1, wherein the anode electrolyte liquid and the cathode electrolyte liquid of the flow battery comprise an active material that is a metal ion having three or more different oxidation numbers.

### Claim 3 (depends on 2)

The method for regenerating the electrolyte liquid of the flow battery of claim 2, wherein the active material is selected from the group consisting of vanadium ions, titanium ions, chromium ions, manganese ions, iron ions, niobium ions, molybdenum ions, silver ions, tantalum ions and tungsten ions.

### Claim 4 (depends on 1)

The method for regenerating the electrolyte liquid of the flow battery of claim 1, wherein, after the stopping of the operation of the flow battery, the cathode electrolyte liquid includes V4+ and the anode electrolyte liquid includes V3+.

### Claim 5 (depends on 4)

The method for regenerating the electrolyte liquid of the flow battery of claim 4, wherein the oxidizing or reducing electrically reduces the mixed electrolyte liquid when the mixed electrolyte liquid has an average oxidation number of greater than 3.5, and electrically oxidizes the mixed electrolyte liquid when the mixed electrolyte liquid has an average oxidation number of less than 3.5.

### Claim 6 (depends on 1)

The method for regenerating the electrolyte liquid of the flow battery of claim 1, wherein the oxidizing or reducing includes 1) electrically oxidizing or reducing the mixed electrolyte liquid; 2) measuring an open circuit voltage (OCV) of the regenerated electrolyte liquid; and 3) repeating 1) and 2) until the measured open circuit voltage is within ±5% of a reference open circuit voltage when comparing with the reference open circuit voltage.

### Claim 7 (depends on 4)

The method for regenerating the electrolyte liquid of the flow battery of claim 4, wherein the oxidizing or reducing includes measuring an average oxidation number of the mixed electrolyte liquid; calculating a charge quantity required to change the measured average oxidation number to an average oxidation number of 3.5 valency; and electrically oxidizing or reducing the mixed electrolyte liquid by adding the calculated charge quantity to the mixed electrolyte liquid.

### Claim 8 (depends on 1)

The method for regenerating the electrolyte liquid of the flow battery of claim 1, further comprising, after the dividing, operating the flow battery again.

### Claim 9

A device for regenerating an electrolyte liquid of a flow battery comprising
1) a first flow battery, which comprises:
a first anode;
a first cathode;
a first separator provided between the first anode and the first cathode;
an anode electrolyte liquid storage unit that supplies a first anode electrolyte liquid to the first anode and that stores the first anode electrolyte liquid that is discharged from the first anode;
a cathode electrolyte liquid storage unit that supplies a cathode electrolyte liquid to the first cathode and that stores the cathode electrolyte liquid that is discharged from the first cathode; and
2) a second flow battery for regeneration, which comprises
a second anode cell;
a second cathode cell;
a second separator provided between the second anode cell and the second cathode cell;
a mixed electrolyte liquid storage unit to which, after operating the first flow battery through repeating charge and discharge and then stopping an operation of the first flow battery, the first anode electrolyte liquid and the cathode electrolyte liquid are introduced from the anode electrolyte liquid storage unit and the cathode electrolyte liquid storage unit and mixed to produce a mixed electrolyte liquid; and
an aqueous acid solution storage unit storing an aqueous acid solution comprising sulfuric acid, hydrochloric acid, nitric acid or a mixture thereof,
wherein through an operation of the second flow battery for regeneration, the mixed electrolyte liquid in the mixed electrolyte liquid storage unit is converted to a regenerated electrolyte liquid.

### Claim 10 (depends on 9)

The device for regenerating the electrolyte liquid of the flow battery of claim 9, wherein the mixed electrolyte liquid storage unit is provided with an open circuit voltage measuring unit measuring an open circuit voltage of the mixed electrolyte liquid.

### Claim 11 (depends on 9)

The device for regenerating the electrolyte liquid of the flow battery of claim 9, wherein the mixed electrolyte liquid further includes an acid including sulfuric acid, hydrochloric acid, nitric acid or a mixture thereof, and an electrolyte liquid active material, and a concentration of the acid in the aqueous acid solution in the aqueous acid solution storage unit is greater than or equal to 80% and less than or equal to 120% with respect to a sum of a concentration of the acid of the mixed electrolyte liquid and a concentration of the electrolyte liquid active material.