Coated carbon nanotube array electrodes

• US 20030143453A1
• Filed: 11/27/2002
• Published: 07/31/2003
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: Trustees of Boston College (Boston College)
• Original Assignee: Trustees of Boston College (Boston College)
• Inventors: Wen, Jian, Chen, Jinghua, Ren, Zhifeng, Huang, Zhongping, Wang, Dezhi
• Granted Patent: US 7,147,966 B2
• Time in Patent Office: Days
• US Class Current: 429/40
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: 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
• CPC Class Codes: H01G 11/36 Nanostructures, e.g. nanofibres, nanotubes or fullerenes
• CPC Class Codes: H01G 11/38 Carbon pastes or blends; Binders or additives therein
• CPC Class Codes: H01G 11/48 Conductive polymers
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/137 Electrodes based on electro-active polymers
• CPC Class Codes: H01M 4/366 as layered products
• CPC Class Codes: H01M 4/583 Carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/602 Polymers
• CPC Class Codes: H01M 4/663 containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• CPC Class Codes: H01M 4/96 Carbon-based electrodes
• CPC Class Codes: H10K 85/221 Carbon nanotubes
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/857 including coating
• CPC Class Codes: Y10S 977/948 : Energy storage/generating using nanostructure, e.g. fuel cell, battery

Abstract

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Claims

1. A conductive carbon nanotube electrode material comprising:

a carbon nanotube substrate comprising a plurality of aligned carbon nanotubes arranged in a three-dimensional array; and

a surface coating comprising an electrically conductive material that is present as a film on the surface of the individual carbon nanotubes in the array,

wherein a majority of said carbon nanotubes are randomly aligned within a series of mutually parallel planes in a manner so as to be packed densely enough to produce multiple points of contact thereamong, whereby electrical continuity is established throughout said three-dimensional array.

2. The conductive carbon nanotube electrode material of claim 1 wherein the carbon nanotubes have a substantially linear configuration.

3. The conductive carbon nanotube electrode material of claim 1 wherein the carbon nanotubes have a substantially cylindrical, hollow core morphology.

4. The conductive carbon nanotube electrode material of claim 1 wherein the carbon nanotubes have a stacked conical segment morphology.

5. The conductive carbon nanotube electrode material of claim 1 wherein the carbon nanotubes have diameters ranging from 30 and 100 nanometers.

6. The conductive carbon nanotube electrode material of claim 1 wherein the carbon nanotubes have lengths ranging from 5 to 10,000 nanometers.

7. The conductive carbon nanotube electrode material of claim 1 wherein the electrically conductive material is an electrically conducting polymer.

8. The electrically conducting polymer of claim 7 which is an organic or organo-metallic polymer.

9. The electrically conducting polymer of claim 7 which is polypyrrole, polyaniline, polythiophene, polyacetylene or derivatives and combinations thereof.

10. The electrically conducting polymer of claim 7 wherein the electrically conducting polymer is polypyrrole.

11. The conductive carbon nanotube electrode material of claim 1 wherein the electrically conducting material further comprises a dopant.

12. The conductive carbon nanotube electrode material of claim 1 wherein the surface coating has a film thickness ranging from 1 to 2,000 nanometers.

13. The carbon nanotube electrode material of claim 10 wherein the coating has a thickness ranging from 50 nanometers to 200 nanometers.

14. The conductive carbon nanotube electrode material of claim 1 wherein a plurality of carbon nanotubes form a free standing aggregate.

15. The conductive carbon nanotube electrode material of claim 14 wherein the free standing aggregate comprises a plurality of carbon nanotubes that are substantially aligned with one another along their longitudinal axis.

16. A carbon nanotube electrode comprising a conductive carbon nanotube electrode material of claim 1 wherein a majority of said nanotubes are randomly aligned within a series of mutually parallel planes in a manner so as to be packed densely enough to produce multiple points of contact thereamong, whereby electrical continuity is established throughout said three-dimensional array.

17. The carbon nanotube electrode of claim 16 further comprising a plurality of carbon nanotubes that packed together in the form of an aggregate that is cohesively bound together by the electrically conductive coating material so as to enable said aggregate to exist in a free-standing form.

18. The carbon nanotube electrode material of claim 17 wherein the electrically conductive coating material is polypyrrole.

19. An electrical energy storage device comprising:

an electrically conducting carbon nanotube electrode comprising a plurality of carbon nanotubes in a three-dimensional array; and

an electrically conducting material that is present as a uniform surface coating on the surface of individual nanotubes,

wherein a majority of said nanotubes are randomly aligned within a series of mutually parallel planes in a manner so as to be packed densely enough to produce multiple points of contact thereamong, whereby electrical continuity is established throughout said three-dimensional array.

20. The electrical storage device of claim 19 wherein the electrical storage device is a battery, an energy storage cell, a sensor, a light-emitting diode, a capacitor, or an electrochromic display.

21. The electrical storage device of claim 20 which is a rechargable battery.

22. A method of preparing an electrically conductive aligned carbon nanotube array comprising the steps of:

contacting a carbon nanotube substrate comprising a plurality of substantially linear mutually aligned carbon nanotubes with a monomeric compound capable of forming an electrically conducting polymeric material that is dissolved in an aqueous or organic solvent containing an electrolyte material such that said carbon nanotube substrate functions as a first electrode in an electrochemical cell;

introducing a second electrode material to form a second electrode in the electrochemical cell; and

applying an electrical potential between the first electrode and the second electrode to cause an electrochemical polymerization of the monomeric compound to the corresponding electrically conducting polymer whereby said electrically conducting polymer provides an adherent surface coating on the individual carbon nanotubes.

23. The method of claim 22 wherein the electrochemical polymerization of the monomeric compound occurs directly on the surface of individual carbon nanotube.

24. The method of claim 22 further comprising the step of pre-treating the carbon nanotube substrate material with an acid solution.

25. The method of claim 24 wherein the acid solution is an aqueous solution of nitric acid, sulfuric acid, chromic acid, an organic per acid or mixtures thereof.

26. The method of claim 24 wherein the acid solution is an aqueous solution of nitric acid.

27. The method of claim 26 wherein the acid solution contains nitric acid ranging from 5 to 50% by weight.