# US 2018/0323445 A1 · Electrode for redox flow battery

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- Number: US 2018/0323445 A1
- Document ID: US20180323445A1
- Status: Published application
- Kind: A1
- Application number: 15/775,676
- Filed: 2016-11-09
- Published: 2018-11-08
- Earliest claimed: 2015-11-13
- Applicants: Avalon Battery (Canada) Corporation
- Inventors: Che-Nan Sun; David Genders; Peter Symons
- Web page: https://patentgrep.com/patent/US20180323445A1

## CPC

- H01M 4/96: Carbon-based electrodes
- H01M 4/0419: {involving spraying}
- H01M 4/0438: {by electrochemical processing (electroless electrochemical plating C23C18/54)}
- H01M 4/0471: {involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis}
- H01M 4/8846: {Impregnation}
- 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}
- 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

Porous carbon felt electrodes for a redox flow battery can be improved by suitably oxidizing the porous carbon felt or by oxidizing carbon particles impregnated into the porous carbon felt. The electrode resistance and voltage efficiency of cells comprising such electrodes can be substantially improved. The invention is particularly suitable for use in vanadium redox flow batteries.

## Claims

### Claim 1

An electrode for a redox flow battery comprising:
a sheet of porous carbon felt;
carbon particles impregnated into the porous carbon felt; and
ionomer impregnated into the porous carbon felt;
characterized in that the carbon particles are oxidized such that they are wettable by water.

### Claim 2 (depends on 1)

The electrode of claim 1 wherein the porous carbon felt is oxidized at a temperature above 500° C.

### Claim 3 (depends on 2)

The electrode of claim 2 wherein the carbon felt is oxidized in air at 600° C. for about 20 minutes.

### Claim 4 (depends on 1)

The electrode of claim 1 wherein the carbon felt is less than or about 3 mm thick.

### Claim 5 (depends on 1)

The electrode of claim 1 wherein the carbon felt is a pyrolyzed polyacrylonitrile felt.

### Claim 6 (depends on 1)

The electrode of claim 1 wherein the carbon particles are carbon black or activated carbon.

### Claim 7 (depends on 1)

The electrode of claim 1 wherein the carbon particles are oxidized by a method selected from chemical treatment, thermal treatment, and electrochemical treatment.

### Claim 8 (depends on 7)

The electrode of claim 7 wherein the carbon particles are oxidized by a chemical treatment method comprising exposing the carbon particles to 1M ammonium persulfate at 70° C.

### Claim 9 (depends on 7)

The electrode of claim 7 wherein the carbon particles are oxidized by a thermal treatment method comprising exposing the carbon particles to air in a range between about 350 and 750° C.

### Claim 10 (depends on 7)

The electrode of claim 7 wherein the specific loading of the impregnated carbon particles to the sheet of carbon felt is in the range from about 0.5 to 2.3 mg/cm2.

### Claim 11 (depends on 1)

The electrode of claim 1 wherein the ionomer is a perfluorosulfonic acid polymer.

### Claim 12 (depends on 1)

The electrode of claim 1 wherein the weight ratio of the ionomer to the carbon particles is less than or about 0.05.

### Claim 13 (depends on 1)

A redox flow battery comprising the electrode of claim 1.

### Claim 14 (depends on 13)

The redox flow battery of claim 13 wherein the battery is a vanadium redox flow battery.

### Claim 15 (depends on 1)

A method for making the electrode of claim 1 comprising:
obtaining the sheet of porous carbon felt, the oxidized carbon particles and the ionomer;
preparing a mixture of the oxidized carbon particles, the ionomer, and a solvent;
impregnating the mixture into the porous carbon felt; and
removing the solvent from the impregnated porous carbon felt.

### Claim 16 (depends on 15)

The method of claim 15 wherein the impregnating step comprises soaking the porous carbon felt in the mixture.

### Claim 17 (depends on 15)

The method of claim 15 wherein the impregnating step comprises spraying the porous carbon felt with the mixture.

### Claim 18 (depends on 15)

The method of claim 15 wherein the impregnating step comprises painting or mechanically coating the porous carbon felt with the mixture.