# US 10,483,581 B2 · Electrochemical energy storage systems and methods featuring large negative half-cell potentials

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- Number: US 10,483,581 B2
- Document ID: US10483581B2
- Status: Granted
- Kind: B2
- Application number: 15/387,594
- Filed: 2016-12-21
- Published: 2017-04-06
- Granted: 2019-11-19
- Earliest claimed: 2012-07-27
- Assignees: Lockheed Martin Energy, LLC
- Applicants: Lockheed Martin Energy, LLC
- Inventors: Arthur J. Esswein; Steven Y. Reece; John Goeltz; Evan R. King; Desiree Amadeo; Nitin Tyagi; Thomas D. Jarvi
- Web page: https://patentgrep.com/patent/US10483581B2

## CPC

- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01M 4/96: Carbon-based electrodes
- H01M 8/04276: Arrangements for managing the electrolyte stream, e.g. heat exchange
- H01M 8/20: Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence)
- H02J 7/865: {Battery or charger load switching, e.g. concurrent charging and load supply (H02J7/50 takes precedence)}
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

The invention concerns flow batteries comprising: a first half-cell comprising: (i) a first aqueous electrolyte comprising a first redox active material; and a first carbon electrode in contact with the first aqueous electrolyte; (ii) a second half-cell comprising: a second aqueous electrolyte comprising a second redox active material; and a second carbon electrode in contact with the second aqueous electrolyte; and (iii) a separator disposed between the first half-cell and the second half-cell; the first half-cell having a half-cell potential equal to or more negative than about −0.3 V with respect to a reversible hydrogen electrode; and the first aqueous electrolyte having a pH in a range of from about 8 to about 13, wherein the flow battery is capable of operating or is operating at a current density at least about 25 mA/cm2.

## Claims

### Claim 1

A flow battery comprising:
a first half-cell comprising:
a first aqueous electrolyte comprising a first redox active material at a concentration in a range of from 0.75 M to about 2.5 M, and a first carbon electrode in contact with the first aqueous electrolyte, the first electrolyte having a pH in the range of from 8 to 13;
a second half-cell comprising:
a second aqueous electrolyte comprising a second redox active material, and a second carbon electrode in contact with the second aqueous electrolyte; and
a separator disposed between the first half-cell and the second half-cell;
wherein the first half-cell has a half-cell potential ranging between −0.3 V and −0.7 V with respect to a reversible hydrogen electrode, and
the first redox active material exhibits substantially reversible electrochemical kinetics; wherein
the half-cell potential is the average measured potential of forward and reverse peaks of a cyclic voltammogram of the first aqueous electrolyte, when measured using an ex-situ apparatus using a flat glassy carbon disc electrode at a scan rate of 100 mV/s; and wherein
substantially reversible electrochemical kinetics refers to a condition in which the first aqueous electrolyte exhibits a voltage difference between the anodic and cathodic peaks of less than 0.3 V, when measured by cyclic voltammetry using an ex-situ apparatus using a flat glassy carbon disc electrode at a scan rate of 100 mV/s.

### Claim 2 (depends on 1)

The flow battery of claim 1, wherein the flow battery is capable of operating at a current density ranging between 25 mA/cm2 and 500 mA/cm2.

### Claim 3 (depends on 2)

The flow battery of claim 2, wherein the flow battery is capable of operating with a current efficiency of at least 50% at a current density ranging between 50 mA/cm2 and 500 mA/cm2.

### Claim 4 (depends on 2)

The flow battery of claim 2, wherein the flow battery is capable of operating with a current efficiency of at least 85% at a current density ranging between 50 mA/cm2 and 500 mA/cm2.

### Claim 5 (depends on 1)

The flow battery of claim 1, wherein the flow battery is capable of operating with a current efficiency of at least 50%.

### Claim 6 (depends on 1)

The flow battery of claim 1, wherein the flow battery is capable of operating with a current efficiency of at least 85%.

### Claim 7 (depends on 1)

The flow battery of claim 1, wherein the flow battery has an open circuit voltage ranging between 1.48 V and 1.95 V, when the flow battery exists at a 50% state-of-charge.

### Claim 8 (depends on 1)

The flow battery of claim 1, wherein the redox active materials do not plate onto the carbon electrodes during operation of the flow battery.

### Claim 9 (depends on 1)

The flow battery of claim 1, wherein at least the first redox active material is a metal ligand coordination compound.

### Claim 10 (depends on 9)

The flow battery of claim 9, wherein both the first redox active material and the second redox active material are metal ligand coordination compounds.

### Claim 11 (depends on 9)

The flow battery of claim 9, wherein the first redox active material is a metal ligand coordination compound comprising titanium.

### Claim 12 (depends on 11)

The flow battery of claim 11, wherein the second redox active material is a hexacyanide metal ligand coordination compound.

### Claim 13 (depends on 1)

The flow battery of claim 1, wherein the separator comprises an ionomer.

### Claim 14 (depends on 1)

The flow battery of claim 1, wherein the second half-cell has a potential ranging between +1.10 V and +2.0 V versus a reversible hydrogen electrode.

### Claim 15 (depends on 1)

The flow battery of claim 1, wherein each redox active material exhibits substantially reversible electrochemical kinetics.

### Claim 16 (depends on 1)

A system comprising the flow battery of claim 1, and further comprising:
a first chamber containing the first aqueous electrolyte and a second chamber containing the second aqueous electrolyte;
at least one electrolyte circulation loop in fluidic communication with each chamber, the at least one electrolyte circulation loop comprising storage tanks and piping for containing and transporting the first and second aqueous electrolytes; and
a power conditioning unit.

### Claim 17 (depends on 1)

The flow battery of claim 1, wherein the first redox active material at a concentration in a range of from 1 M to about 2.5 M.

### Claim 18 (depends on 1)

The flow battery of claim 1, wherein the first half-cell has a half-cell potential ranging between −0.35 V and −0.7 V with respect to a reversible hydrogen electrode, and the first redox active material does not substantially plate onto the carbon electrode during operation of the flow battery.

### Claim 19 (depends on 1)

The flow battery of claim 1, wherein the first half-cell has a half-cell potential ranging between −0.4 V and −0.7 V with respect to a reversible hydrogen electrode, and the first redox active material does not substantially plate onto the carbon electrode during operation of the flow battery.

### Claim 20 (depends on 1)

The flow battery of claim 1, wherein the first half-cell has a half-cell potential ranging between −0.5 V and −0.7 V with respect to a reversible hydrogen electrode, and the first redox active material does not substantially plate onto the carbon electrode during operation of the flow battery.