# US 6,781,817 B2 · Fringe-field capacitor electrode for electrochemical device

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- Number: US 6,781,817 B2
- Document ID: US6781817B2
- Status: Granted
- Kind: B2
- Application number: 10/398,698
- Filed: 2003-04-02
- Published: 2004-01-22
- Granted: 2004-08-24
- Earliest claimed: 2000-10-02
- Assignees: Biosource, Inc.
- Inventors: Marc D. Andelman
- Web page: https://patentgrep.com/patent/US6781817B2

## CPC

- C02F 1/4691: {Capacitive deionisation}
- H01G 11/24: characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
- H01G 11/26: characterised by their structure, e.g. multi-layered, porosity or surface features
- H01G 11/36: Nanostructures, e.g. nanofibres, nanotubes or fullerenes
- H01G 11/38: Carbon pastes or blends; Binders or additives therein
- H01G 11/42: Powders or particles, e.g. composition thereof
- H01M 4/583: Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M 4/8605: {Porous electrodes}
- H01M 4/925: {supported on carriers, e.g. powder carriers}
- H01M 4/96: Carbon-based electrodes
- C02F 2001/46152: {characterised by the shape or form}
- H01M 8/00: Fuel cells; Manufacture thereof
- Y02E 60/10: Energy storage using batteries
- Y02E 60/13: Energy storage using capacitors
- Y02E 60/50: Fuel cells
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- 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 invention features an electrochemical device which includes at least two capacitor electrodes 16, each of which includes a conductive material characterized in that at least ten percent (10%) of the overall surface area of the conductive material is an edge plane. In contrast to a basal plane, the electric field along an edge plane is distorted so as to exhibit an ‘edge effect or ‘fringe effect. Capacitor electrodes 16 with many edges, points, corners, or fractal surfaces exhibit greater capacitance per unit volume or mass amount of capacitor electrode material, than do materials in which the surface area of the material is predominately basal plane. An electrochemical device of the invention can be, for example, an electrochemical cell, e.g., a battery, a capacitor, or a flow-through capacitor.

## Claims

### Claim 1

An electrochemical device comprising at least two capacitor electrodes, each of said two capacitor electrodes comprising a conductive material characterized in that at least 10% of the surface area of said conductive material is an edge plane.

### Claim 2 (depends on 1)

The electrochemical device of claim 1, wherein said electrochemical device is a flow-through capacitor.

### Claim 3 (depends on 2)

The electrochemical device of claim 2, wherein said electrochemical device has a single electrode capacitance of at least 20 farads per cubic centimeter of electric material.

### Claim 4 (depends on 2)

The electrochemical device of claim 2, wherein said electrochemical device has a single electrode capacitance of at least 5 microfarads per square centimeter of surface area.

### Claim 5 (depends on 4)

The electrochemical device of claim 4, wherein said conductive material comprises particles of less than 10 microns in diameter.

### Claim 6 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material has a surface area of between 20 and 3000 square meters per gram material.

### Claim 7 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material is selected from the group consisting of pyrolytic graphite and graphite particles.

### Claim 8 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material is selected from the group consisting of nanofibers, nanotubes, and carbon fibers of less than 100 microns in diameter.

### Claim 9 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material is selected from the group consisting of carbon black and carbon nanoparticles.

### Claim 10 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material is selected from the group consisting of activated carbon and carbon powder.

### Claim 11 (depends on 5)

The electrochemical device of claim 5, wherein said conductive material is selected from the group consisting of mechanically aligned graphite.

### Claim 12 (depends on 4)

The electrochemical device of claim 4, wherein said edge planes are protected by boron or phosphorous.

### Claim 13 (depends on 4)

The electrochemical device of claim 4, wherein said conductive material is a nanofiber of less than 300 nanometers in diameter.

### Claim 14 (depends on 2)

The electrochemical device of claim 2, wherein said capacitor electrode further comprises a binder material.

### Claim 15 (depends on 14)

The electrochemical device of claim 14, wherein said binder material is selected from the group consisting of latex and a phenolic resin.

### Claim 16 (depends on 14)

The electrochemical device of claim 14, wherein said binder material is a perfluorocarbon.

### Claim 17 (depends on 14)

The electrochemical device of claim 14, wherein said binder material is a polymer fiber.

### Claim 18 (depends on 14)

The electrochemical device of claim 14, wherein said binder material is a polytetrafluoroethylene (PTFE) polymer.

### Claim 19 (depends on 14)

The electrochemical device of claim 14, wherein said binder material is in the form of a flexible sheet of less than 0.03 inches thick.

### Claim 20 (depends on 2)

The electrochemical device of claim 2, wherein said electrochemical device further comprises a current collector, and said capacitor electrode is either integral with, or in the same plane as, said current collector.

### Claim 21 (depends on 2)

The electrochemical device of claim 2, wherein one or more of the edge planes of said conductive material are located on one or more of a branch, a dendrite, a fork, a jagged edge, a fractal edge, a point, a spine, or a protrusion in said conductive material.

### Claim 22 (depends on 2)

The electrochemical device of claim 2, wherein said conductive material is a laminate comprising graphite, and said graphite is electrically integral with said current collector.

### Claim 23 (depends on 2)

The electrochemical device of claim 2, wherein said electrochemical device further comprises a spacer layer, and said flow-through capacitor has a series resistance of less than 30 ohms per square centimeter of spacer layer.

### Claim 24 (depends on 2)

The electrochemical device of claim 2, wherein said capacitor electrode comprises one or more pores through which an aqueous, conductive solution can pass through said capacitor electrode, and said edge planes of said conductive material are located on the surface of said pores.

### Claim 25 (depends on 2)

The electrochemical device of claim 2, wherein said flow-through capacitor is used to remove ions from an aqueous medium so as to purify said aqueous medium, and said flow-through capacitor is able to remove at least 90% of said ions when said medium is a solution of 0.01M NaCl, said conductive material in said capacitor electrode is carbon, and said solution is allowed to flow through said flow-through capacitor at a flow rate of at least one milliliter per minute per gram of carbon at 2 volts.

### Claim 26 (depends on 2)

A method of removing ions from an aqueous medium, said method comprising the steps of:
(a) providing the flow-through capacitor of claim 2;
(b) allowing an electric current to flow between two capacitor electrodes of said flow-through capacitor; and
(c) allowing a source of aqueous medium to flow through said flow-through capacitor so as to remove said ions from said medium.

### Claim 27 (depends on 26)

The method of claim 26, wherein said method is able to remove at least 90% of said ions when said medium is a solution of 0.01M NaCl, said conductive material in said capacitor electrode is carbon, and said solution is allowed to flow through said flow-through capacitor at a flow rate of at least one milliliter per minute per gram of carbon at 2 volts.

### Claim 28

A method of making an electrochemical device, said method comprising the steps of:
(a) providing at least two capacitor electrodes, wherein each of said two capacitor electrodes comprise a conductive material characterized in that at least 10% of the surface area of said conductive material is edge plane; and
(b) positioning a source of electrical current so as to provide electrical communication between each of said two capacitor electrodes.

### Claim 29 (depends on 28)

The method of claim 28, wherein said capacitor electrode has a capacitance of at least 20 farads per cubic centimeter of electrical material.

### Claim 30 (depends on 28)

The method of claim 28, wherein said capacitor electrodes have a single electrode capacitance of at least 5 microfarads per square centimeter of surface area.

### Claim 31 (depends on 28)

The method of claim 28, further comprising the step of mixing said conductive material with a binder material.

### Claim 32 (depends on 31)

The method of claim 31, further comprising the step of forming said binder material into a flexible sheet of less than 0.03 inch thickness, said forming selected from the group consisting of extruding, calendaring, pressing, adhering said sheet onto a current collector, and spray coating.