# US 8,541,138 B2 · Perfluorinated membranes and improved electrolytes for redox cells and batteries

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- Number: US 8,541,138 B2
- Document ID: US8541138B2
- Status: Granted
- Kind: B2
- Application number: 11/917,989
- Filed: 2006-06-19
- Published: 2008-11-27
- Granted: 2013-09-24
- Earliest claimed: 2005-06-20
- Assignees: NewSouth Innovations Pty Limited
- Applicants: George Christopher Kazacos; Nicholas Michael Kazacos
- Inventors: George Christopher Kazacos; Nicholas Michael Kazacos
- Web page: https://patentgrep.com/patent/US8541138B2

## CPC

- H01M 8/109: {thermal other than drying, e.g. sintering}
- B60L 50/64: Constructional details of batteries specially adapted for electric vehicles
- H01M 8/1023: having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
- H01M 8/1067: characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
- H01M 8/1081: starting from solutions, dispersions or slurries exclusively of polymers
- H01M 8/1088: Chemical modification, e.g. sulfonation
- H01M 8/20: Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence)
- B60L 2240/545: Temperature
- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01M 10/0565: Polymeric materials, e.g. gel-type or solid-type
- Y02E 60/10: Energy storage using batteries
- Y02E 60/50: Fuel cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- Y02T 90/16: Information or communication technologies improving the operation of electric vehicles
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

The present invention describes an improved membrane for Redox Flow Batteries, in particular for Vanadium Redox Batteries and energy storage systems and applications employing the Vanadium Redox Cells and Batteries. Redox Flow Batteries involve the use of two redox couple electrolytes separated by an ion exchange membrane that is the most important cell component.

## Claims

### Claim 1

A redox cell comprising:
a positive half-cell in communication with a positive half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (III), vanadium (IV) and vanadium (V);
a negative half-cell in communication with a negative half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (II), vanadium (III) and vanadium (IV); and
a cast perfluorinated ionically conducting membrane located between the positive half cell and the negative half cell and in contact with the positive half cell solution and the negative half cell solution and wherein the perfluorinated membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and a perfluorosulphonic acid/PTFE copolymer, said membrane having isotropic swelling and tensile strength properties, a conductivity at 25° C. of between 0.01 and 1 S/cm, and having a linear expansion of less than 8% in both directions from 50% Relative Humidity at 23° C. to water soaked at 23° C.

### Claim 2 (depends on 1)

The redox cell according to claim 1, wherein the perfluorinated ionically conducting membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and perfluorosulphonic acid/PTFE copolymer in acid form.

### Claim 3 (depends on 1)

The redox cell according to claim 1, wherein the perfluorinated ionically conducting membrane has a thickness of between 0.5 and 5 mil, an acid capacity of between 0.5 and 2 mmol/g, a conductivity at 25° C. of between 0.01 and 1 S/cm, a water uptake of between 30% and 70% at 100° C. for 1 hour, a tensile strength of between 20 and 60 MPa and a melting point ranging from 180 to 240° C.

### Claim 4 (depends on 1)

The redox cell of according to claim 1, wherein the membrane comprises microparticles which increase water uptake and conductivity and which decrease linear expansion of the membrane.

### Claim 5

A process for making a redox cell comprising a positive half-cell in communication with a positive half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (III), vanadium (IV) and vanadium (V); a negative half-cell in communication with a negative half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (II), vanadium (III) and vanadium (IV); and a cast perfluorinated ionically conducting membrane located between the positive half cell and the negative half cell and in contact with the positive half cell solution and the negative half cell solution and wherein the perfluorinated membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and a perfluorosulphonic acid/PTFE copolymer, said membrane having isotropic swelling and tensile strength properties, a conductivity at 25° C. of between 0.01 and 1 S/cm, and having a linear expansion selected from the group consisting of less than 8%, less than 5% and less than 3% in both directions from 50% Relative Humidity at 23° C. to water soaked at 23° C.,
said process comprising:
treating a cast perfluorinated ionically conducting membrane prior to use in the redox cell by soaking the membrane in an aqueous solution to reduce resistivity of the membrane and enhance voltage efficiency during the charge-discharge cycling of the redox celltreating the membrane prior to use in the redox cell by soaking the membrane in an aqueous solution to reduce resistivity of the membrane and enhance voltage efficiency during the charge-discharge cycling of the redox cell;
locating the membrane between and in contact with a positive half cell and a negative half cell, and introducing a positive half cell solution into the positive half cell and a negative half cell solution into the negative half cell, wherein:
the positive half cell solution contains at least one vanadium ion selected from the group consisting of vanadium (III), vanadium (IV) and vanadium (V);
the negative half cell solution contains at least one vanadium ion selected from the group consisting of vanadium (II), vanadium (III) and vanadium (IV); and
the perfluorinated ionically conducting membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and a perfluorosulphonic acid/PTFE copolymer.

### Claim 6 (depends on 5)

The process of claim 5, wherein treating the membrane is carried out at above room temperature.

### Claim 7 (depends on 6)

The process of claim 6, wherein treating the membrane is conducted in a process having at least one step and in at least one aqueous solution.

### Claim 8 (depends on 7)

The process of claim 7, wherein the aqueous solution is selected from the group consisting of hydrogen peroxide, HCl, NaOH and sulphuric acid.

### Claim 9 (depends on 5)

The process of claim 5 further comprising boiling the membrane in water prior to use in the redox cell in order to reduce resistivity of the membrane and enhance voltage efficiency during the charge-discharge cycling of the redox cell.

### Claim 10 (depends on 1)

The redox cell according to claim 1, wherein the positive half-cell solution includes a first supporting electrolyte selected from the group H2SO4, HBr and HBr/HCl mixtures, and the negative half-cell solution includes a second supporting electrolyte selected from H2SO4, HBr and HBr/HCl mixtures.

### Claim 11 (depends on 1)

The redox cell according to claim 1, wherein the vanadium (III) ions and the vanadium (IV) ions in both the positive half cell solution and the negative half cell solution are in a V(III):V(IV) molar ratio of substantially 1:1 and wherein a ratio of volume of the negative half cell solution to a volume of the positive half cell solution is substantially 1:1.

### Claim 12 (depends on 10)

The redox cell according to claim 10, wherein:
the positive half cell solution includes at least one ion selected from the group V(V) ions, Br3− ions and Br2Cl− ions;
the negative half cell solution includes at least one ion selected from the group vanadium (II) ions and vanadium (III).

### Claim 13 (depends on 10)

The redox cell according to claim 10, wherein the first supporting electrolyte and the second supporting electrolyte are independently selected from the group consisting of H2SO4, HBr and HBr/HCl mixtures and wherein vanadium ion concentration in both the first supporting electrolyte and the second supporting electrolyte is between 1 and 3M.

### Claim 14 (depends on 13)

The redox cell according to claim 13, wherein the vanadium ion concentration is between 2 and 3M.

### Claim 15 (depends on 13)

The redox cell according to claim 13, wherein total supporting electrolyte concentration in both the first supporting electrolyte and the second supporting electrolyte is between 2 and 10M.

### Claim 16 (depends on 13)

The redox cell according to claim 13, wherein the first supporting electrolyte and the second supporting electrolyte are each H2SO4 and the total sulphate concentration is 4-5M and wherein the vanadium concentration is 1-2M in both the first supporting electrolyte and the second supporting electrolyte.

### Claim 17 (depends on 13)

The redox cell according to claim 13, wherein the first supporting electrolyte and the second supporting electrolyte are each HBr at a concentration between 4 and 9M.

### Claim 18 (depends on 13)

The redox cell according to claim 13, wherein the first supporting electrolyte and the second supporting electrolyte each contain HCl at a concentration of 0.1 to 3M.

### Claim 19 (depends on 17)

The redox cell according to claim 17, wherein the first supporting electrolyte and the second supporting electrolyte each contain HC1 at a concentration of 0.1 to 3M and a complexing agent to bind bromine.

### Claim 20 (depends on 19)

The redox cell according to claim 19, wherein the complexing agent is selected from at least one of a group consisting of N-ethyl-N-methylpyrrolidiniumbromide (MEP), N-ethyl-N-methylmorpholiniumbromide (MEM).

### Claim 21 (depends on 1, 13)

A method for using the redox cell of claim 13 in refueling an electric vehicle, said method comprising the steps of:
draining discharged positive half cell solution and discharged negative half cell solution from the positive and negative half cells respectively of a first redox cell according to claim 1 into external storage tanks, said redox cell being mounted on the vehicle;
pumping said solutions through a second, external charging, redox cell according to claim 1, said second redox cell being powered by a power source selected from the group consisting of grid power, diesel generated power, wind generated power, wave generated power, solar energy from photovoltaic arrays;
recharging the positive and negative half cell solutions; and
re-using said positive and negative half cell solutions in the first redox cell.

### Claim 22 (depends on 1)

The redox cell of claim 1, wherein the positive half-cell is rebalanced with the negative half-cell so as to restore capacity loss due to gassing reactions and air oxidation of the negative half-cell during charge-discharge cycling, wherein the positive half-cell comprises a pre-determined quantity of an oxidizable organic compound periodically added to partially reduce the V(V) or polyhalide ions and restore capacity.

### Claim 23 (depends on 22)

The redox cell of claim 22, wherein the oxidizable organic compound is such that the product of an oxidation reaction is carbon dioxide and water.

### Claim 24 (depends on 23)

The redox cell according to claim 23, wherein the oxidizable organic compound is selected from the group consisting of ethanol and methanol.

### Claim 25 (depends on 1)

A method for chemically regenerating the redox cell of claim 1, comprising adding hydrogen peroxide to the positive half-cell.