Carbon Nanotube Based Pastes

• US 20110171364A1
• Filed: 01/13/2011
• Published: 07/14/2011
• Est. Priority Date: 01/13/2010
• Status: Active Grant

• Current Assignee: Cnano Technology Limited
• Original Assignee: Cnano Technology Limited
• Inventors: Tsai, Ching-Jung, Wei, Zhaojie, Li, Qi, Xing, Caihong, Ma, Jun, Wang, Jianfeng
• Granted Patent: US 8,540,902 B2
• Time in Patent Office: Days
• US Class Current: 427/77
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C08K 3/041 Carbon nanotubes
• CPC Class Codes: C09D 139/06 Homopolymers or copolymers of N-vinyl-pyrrolidones
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: C09D 7/45 Anti-settling agents
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: C09D 7/67 Particle size smaller than 100 nm
• CPC Class Codes: C09D 7/70 characterised by shape, e.g. fibres, flakes or microspheres
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01M 4/625 Carbon or graphite
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Carbon-nanotube based pastes and methods for making and using the same are disclosed. Carbon nanotubes are dispersed via milling; resultant paste has Hegman scale of greater than 7. The pastes can be used as electro-conductivity enhancement in electronic devices such as batteries, capacitors, electrodes or other devices needing high conductivity paste.

Claims

1. A paste composition comprising:

carbon nanotube agglomerates;

a dispersant; and

a liquid vehicle;

wherein the carbon nanotube agglomerates are dispersed as defined by a Hegman scale reading of 7 or more.

2. The paste composition of claim 1, wherein the carbon nanotubes are multiwall carbon nanotubes.

3. The paste composition of claim 1, wherein the dispersant is selected from a group consisting of poly(vinylpyrrolidone) (PVP), poly(styrene sulfonate) (PSS), poly(phenylacetylene) (PAA), poly(meta-phenylenevinylene) (PmPV), polypyrrole (PPy), poly(p-phenylene benzobisoxazole) (PBO), natural polymers, amphiphilic materials in aqueous solutions, anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), cyclic lipopeptide biosurfactant, surfactin, water-soluble polymers, carboxyl methyl cellulose, hydroxyl ethyl cellulose, poly(vinyl alcohol), PVA, sodium dodecyl sulfate, SDS, polyoxyethylene surfactant, poly(vinylidene fluoride), PVdF, carboxyl methyl cellulose (CMC), hydroxyl ethyl cellulose (HEC), polyacrylic acid (PAA), polyvinyl chloride (PVC) and combinations thereof.

4. The paste composition of claim 1, wherein the dispersant is poly(vinylpyrrolidone).

5. The paste composition of claim 1, wherein the liquid vehicle is selected from a group consisting of water, alcohols, ethers, aromatic hydrocarbons, esters, ketones, n-methyl pyrrolidone and mixtures thereof.

6. The paste composition of claim 1 wherein the paste has a solid state bulk electrical resistivity less than 10⁻

1 Ω

-cm and a viscosity greater than 5,000 cps.

7. The paste composition of claim 1, wherein the carbon nanotube agglomerates have a maximum dimension from about 0.5 to about 1000 micrometers.

8. The paste composition of claim 1, wherein the carbon nanotubes have a diameter from about 4 to about 100 nm.

9. The paste composition of claim 7, wherein the carbon nanotube agglomerates are made in a fluidized bed reactor.

10. The paste composition of claim 1, wherein the carbon nanotube agglomerates have been reduced in size by one or more processes chosen from a group consisting of jet mill, ultra-sonicator, ultrasonics, colloid-mill, ball-mill, bead-mill, sand-mill, dry milling and roll-mill.

11. The paste composition of claim 10, wherein the tap density of the carbon nanotube agglomerates is greater than about 0.02 g/cm³.

12. The paste composition of claim 1, wherein the carbon nanotube agglomerates are present in the range of about 1 to 15% by weight of paste.

13. The paste composition of claim 1, wherein the dispersant is present in the range of 0.2 to about 5% by weight of the paste.

14. The paste composition of claim 1, wherein the ratio of the dispersant weight to carbon nanotube agglomerates weight is less than 1.

15. A method for making a paste composition comprising the steps:

selecting carbon nanotube agglomerates;

adding the carbon nanotubes agglomerates to a liquid vehicle to form a suspension;

dispersing the carbon nanotubes agglomerates in the suspension;

reducing the size of the carbon nanotube agglomerates to a Hegman scale of 7 or less; and

removing a portion of the liquid vehicle from the suspension to form a concentrated paste composition such that the paste composition has carbon nanotubes present in the range of about 1 to 15% by weight, a bulk electrical resistivity of about 10<sup>−

1</sup> Ω

-cm or less and a viscosity greater than 5,000 cps.

16. The method of claim 15 wherein the carbon nanotube agglomerates selected are spherical carbon nanotube agglomerates.

17. The method of claim 15, further comprising the step of mixing a dispersant with the liquid vehicle before adding the carbon nanotube agglomerates.

18. The method of claim 15, wherein the dispersing step is performed by a means for dispersing.

19. A paste composition consisting of;

multi-walled carbon nanotubes of diameter greater than 4 nm;

a dispersant chosen from a group consisting of poly(vinylpyrrolidone) (PVP), poly(styrene sulfonate) (PSS), poly(phenylacetylene) (PAA), poly(meta-phenylenevinylene) (PmPV), polypyrrole (PPy), poly(p-phenylene benzobisoxazole) (PBO), natural polymers, amphiphilic materials in aqueous solutions, anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), cyclic lipopeptide bio surfactant, surfactin, water-soluble polymers, carboxyl methyl cellulose, hydroxyl ethyl cellulose, poly(vinyl alcohol), PVA, sodium dodecyl sulfate, SDS, polyoxyethylene surfactant, poly(vinylidene fluoride), PVdF, carboxyl methyl cellulose (CMC), hydroxyl ethyl cellulose (HEC), polyacrylic acid (PAA), polyvinyl chloride (PVC) and combinations thereof; and

a liquid vehicle chosen from a group consisting of water, alcohols, ethers, aromatic hydrocarbons, esters, ketones, n-methyl pyrrolidone and mixtures thereof such that the paste composition has carbon nanotubes present in the range of about 1 to 15% by weight, a bulk electrical resistivity of about 10<sup>−

1</sup> Ω

-cm or less and a viscosity greater than 5,000 cps.

20. The paste composition of claim 19 further consisting of lithium ion battery electrode materials chosen from a group consisting of lithium, oxygen, phosphorous, sulphur, nitrogen, nickel, cobalt, manganese, vanadium, silicon, carbon, aluminum, niobium and zirconium and iron wherein the paste composition is present in a range from about 2% to about 50% by weight and the viscosity is greater than about 5,000 cps.

21. The paste composition of claim 20 further consisting of a polymeric binder.

22. The paste composition of claim 20 wherein the paste composition is contacting a metallic surface to form an electrode for a lithium ion battery and the liquid vehicle is removed.

23. A method of preparing an battery electrode coating using the paste composition of claim 19 comprising the steps:

mixing the paste composition with lithium ion battery materials;

coating the paste onto a metallic film to form an electrode for a lithium ion battery and removing excess liquid from the coating.

24. The method of claim 23 further comprising the step of mixing a polymeric binder with a liquid vehicle before mixing the paste composition with lithium ion battery materials.

25. The method of claim 23 wherein the polymeric binder is chosen from a group consisting of polyethylene, polypropylene, polyamide, polyurethane, polyvinyl chloride, polyvinylidene fluoride, thermoplastic polyester resins, and mixtures thereof and is less than about 5% by weight of the paste composition.