Aligned graphene-carbon nanotube porous carbon composite

Patent metadata

Field	Value
Publication number	US-2017221645-A1
Application number	US-201515502480-A
Country	US
Kind code	A1
Filing date	Aug 11, 2015
Priority date	Aug 11, 2014
Publication date	Aug 3, 2017
Grant date	—

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

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.

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 .- 6 . (canceled)

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

8 . 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.

9 . 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.

10 . 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.

11 .- 12 . (canceled)

13 . 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.

14 . The method of claim 13 , 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.

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

16 . (canceled)

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

18 . (canceled)

19 . The composite of claim 1 , wherein the porous matrix further comprises an interconnected pore network, extending from an outer surface of the composite to the embedded scaffold.

20 . The composite of claim 19 , wherein a mean diameter of the pores of the pore network decreases with distance from the outer surface of the composite.

21 .- 24 . (canceled)

25 . The composite of claim 13 [[and 14 ]], 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.

26 . (canceled)

27 . 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.

28 . 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; an electrolyte provided between the two electrodes; and a separator mechanically separating the two electrodes.

29 . The electrochemical system of claim 28 , wherein the at least one composite electrode is mounted upon a supporting substrate.

30 .- 34 . (canceled)

35 . The electrochemical system of claim 28 , wherein the electrolyte is a room-temperature ionic liquid.

36 . The electrochemical system of claim 35 , 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).

37 .- 38 . (canceled)

39 . The electrochemical system of claim 28 , wherein the electrode further comprises a lithium compound embedded within the composite.

40 . (canceled)

41 . The electrochemical system of claim 39 , 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.

42 .- 46 . (canceled)

47 . 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.

48 . The method of claim 47 , wherein, after removing the solvents:
the plurality of graphene sheets and the plurality of carbon nanotubes form a three-dimensional scaffold 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

Assignees

• Univ Arizona

Inventors

• Gangopadhyay Palash
• Tan Scott H

Classifications

• H01G11/26

  characterised by their structure, e.g. multi-layered, porosity or surface features · CPC title

• Y10S977/842

  for carbon nanotubes or fullerenes · CPC title

• H01M2300/0045

  Room temperature molten salts comprising at least one organic ion · CPC title

• Y10S977/753

  with polymeric or organic binder · CPC title

• C01B32/194

  After-treatment · CPC title