Aligned graphene-carbon nanotube porous carbon composite

Patent metadata

Field	Value
Publication number	US-10614966-B2
Application number	US-201515502480-A
Country	US
Kind code	B2
Filing date	Aug 11, 2015
Priority date	Aug 11, 2014
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

Embodiments of the present disclosure are directed to carbon-containing composites which are suitable for use as electrodes in electrochemical systems. The composites are formed from a scaffold of graphene and carbon nanotubes. Graphene flakes form a plurality of generally planar sheets (e.g., extending in an x-y plane) separated in the direction of a composite axis (e.g., along a z-axis) and approximately parallel to one another. The carbon nanotubes extend between the graphene sheets and at least a portion of the carbon nanotubes are aligned in approximately the same direction, at a defined angle with respect to the composite axis. At least a portion of the scaffold is embedded within a porous carbon matrix (e.g., an activated carbon, a polymer derived graphitic carbon, etc.).

First claim

What is claimed is:

1. A composite material, comprising:
a scaffold, comprising: a plurality of graphene sheets each oriented in an independent alignment plane substantially perpendicular to a composite axis; and a plurality of carbon nanotubes, wherein at least a portion of the carbon nanotubes are oriented such that their respective tube axes are oriented substantially at a defined angle with respect to the composite axis; and
a matrix comprising a porous carbon, wherein the scaffold is at least partially embedded in the matrix,
wherein the matrix further comprises an interconnected pore network, extending from an outer surface of the composite to the embedded scaffold, and wherein a mean diameter of pores of the pore network decreases with distance from the outer surface of the composite.

2. The composite of claim 1 , further comprising at least two graphene sheets, wherein the plurality of carbon nanotubes extends between the at least two graphene sheets.

3. The composite of claim 2 , wherein the at least two graphene sheets are separated by a distance within the range between about 0.8 nm to about 2000 nm.

4. The composite of claim 1 , wherein the plurality of graphene sheets comprises at least one of single layer graphene, multi-layer graphene, and reduced graphene oxide (RGO).

5. The composite of claim 1 , wherein the plurality of carbon nanotubes are single-walled carbon nanotubes.

6. The composite of claim 1 , wherein a mean outer diameter of the plurality of carbon nanotubes is within the range between about 0.8 nm to about 2 nm.

7. The composite of claim 1 , wherein a mean length of the plurality of carbon nanotubes is within the range between about 2 nm to about 20 nm.

8. The composite of claim 1 , wherein the plurality of carbon nanotubes are functionalized with one or more functional groups selected from the group consisting of carboxylic acid (—COOH), sulphonic acid (—SO 3 H), amine (—NH 2 ), and hydroxyl (—OH) containing groups.

9. The composite of claim 1 , further comprising a binder, wherein the porous carbon is an activated carbon and wherein the binder connects at least a portion of the plurality of graphene sheets to at least a portion of the plurality of carbon nanotubes via the porous carbon matrix.

10. The method of claim 9 , wherein the binder is selected from the group consisting of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polystyrene, styrene-butadiene rubber (SBR), poly(ethylene oxide), functionalized graphene oxide, and silver paste.

11. The composite of claim 1 , wherein the porous carbon is formed from one of carbonized polyacrylonitrile (PAN) and polystyrene.

12. The composite of claim 1 , wherein the plurality of graphene sheets and the plurality of carbon nanotubes are mechanically connected to one another.

13. The composite of claim 9 , wherein the composite comprises:
about 0.1% to about 5% carbon nanotubes;
about 0.1% to about 5% graphene;
about 70% to about 98.8% porous carbon; and
about 1% to about 20% binder;
on the basis of the total weight of the composite.

14. A composite electrode comprising:
a scaffold, comprising:
a plurality of graphene sheets each oriented in an independently alignment plane substantially perpendicular to a composite axis; and
a plurality of carbon nanotubes, wherein at least a portion of the carbon nanotubes are oriented such that their respective tube axes are oriented substantially at a defined angle with respect to the composite axis;
a matrix comprising a porous carbon, wherein the scaffold is at least partially embedded in the matrix,
wherein the matrix further comprises an interconnected pore network, extending from an outer surface of the composite electrode to the embedded scaffold, and wherein a mean diameter of pores of the pore network decreases with distance from the outer surface of the composite electrode.

15. An electrochemical system, comprising:
a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a composite material comprising:
a scaffold, comprising:
a plurality of graphene sheets each oriented in an independent alignment plane substantially perpendicular to a composite axis; and
a plurality of carbon nanotubes, wherein at least a portion of the carbon nanotubes are oriented such that their respective tube axes are oriented substantially at a defined angle with respect to the composite axis;
a matrix comprising a porous carbon, wherein the scaffold is at least partially embedded in the matrix, wherein the matrix further comprises an interconnected pore network, extending from an outer surface of the composite material to the embedded scaffold, and wherein a mean diameter of pores of the pore network decreases with distance from the outer surface of the composite material;
an electrolyte provided between the two electrodes; and
a separator mechanically separating the two electrodes.

16. The electrochemical system of claim 15 , wherein the at least one composite electrode is mounted upon a supporting substrate.

17. The electrochemical system of claim 15 , wherein the electrolyte is a room-temperature ionic liquid.

18. The electrochemical system of claim 17 , wherein the electrolyte is selected from the group consisting of: potassium hydroxide (KOH), sulfuric acid (H 2 SO 4 ), 1-butyl-4-methylpyridinium tetrafluoroborate (4MBPBF 4 ), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIM-OTf), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4 ), sodium sulfate (Na 2 SO 4 ), 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsuphonyl)imide (EMIM-TFSI), N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 -TFSI), and 1-ethyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)azanide (EMIM-TFSA).

19. The electrochemical system of claim 15 , wherein the electrode further comprises a lithium compound embedded within the composite.

20. The electrochemical system of claim 19 , wherein the at least one electrode comprises:
about 0.1% to about 5% carbon nanotubes;
about 0.1% to about 5% graphene;
up to about 2% porous carbon;
about 88% to about 99.8% lithium compound;
on the basis of the total weight of the electrode.

21. A method for fabricating a composite material, comprising:
providing a carbon slurry, the slurry comprising:
a first solvent;
a porous carbon;
a plurality of conductive graphene sheets; and
a plurality of carbon nanotubes;
depositing a film of the carbon slurry upon a substrate;
positioning the carbon slurry film within a magnetic field and sonic wave, wherein the magnetic field lines are oriented at a defined angle with respect to the plane of the substrate and wherein the magnetic field strength is sufficient to induce at least a portion of the carbon nanotubes to orient such that their respective tube axes are substantially parallel to the magnetic field lines; and
removing at least a portion of the solvents from the deposited film to form a solidified film of the composite,
whereinafter removing the solvents:
the plurality of graphene sheets and the plurality of carbon nanotubes form a three-dimensional scaffold at least partially embedded within a matrix formed by the porous carbon,
the plurality of graphene sheets and the plurality of carbon nanotubes are connected to each other via the porous carbon matrix;
the plurality of graphene sheets are oriented in an independent alignment plane

Assignees

• Univ Arizona

Inventors

• Gangopadhyay Palash
• Tan Scott H

Classifications

• H01G11/32

  Carbon-based · CPC title

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• H01G11/24

  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 title

• Y10S977/948

  Energy storage/generating using nanostructure, e.g. fuel cell, battery · CPC title

• C01B2204/04

  Specific amount of layers or specific thickness · CPC title