Supercritical Fluid Production of Graphene-Based Supercapacitor Electrode from Coke or Coal

Patent metadata

Field	Value
Publication number	US-2018019071-A1
Application number	US-201615211522-A
Country	US
Kind code	A1
Filing date	Jul 15, 2016
Priority date	Jul 15, 2016
Publication date	Jan 18, 2018
Grant date	—

Abstract

Provided is a process for producing a graphene-based supercapacitor electrode from a supply of coke or coal powder, comprising: (a) exposing this powder to a supercritical fluid for a period of time in a pressure vessel to enable penetration of the supercritical fluid into internal structure of the coke or coal; wherein the powder is selected from petroleum coke, coal-derived coke, meso-phase coke, synthetic coke, leonardite, anthracite, lignite coal, bituminous coal, or natural coal mineral powder, or a combination thereof; (b) rapidly depressurizing the supercritical fluid at a fluid release rate sufficient for effecting exfoliation and separation of the coke or coal powder to produce isolated graphene sheets, which are dispersed in a liquid medium to produce a graphene suspension; and (c) shaping and drying the graphene suspension to form the supercapacitor electrode having a specific surface area greater than 200 m 2 /g.

First claim

1 . A process for producing a graphene-based supercapacitor electrode from a supply of coke or coal powder containing therein domains of hexagonal carbon atoms and/or hexagonal carbon atomic interlayers with an interlayer spacing, said process comprising:
(a) exposing said supply of coke or coal powder to a supercritical fluid at a first temperature and a first pressure for a first period of time in a pressure vessel to enable penetration of the supercritical fluid into an internal structure of the coke or coal; wherein said coke or coal powder is selected from the group consisting of petroleum coke, coal-derived coke, meso-phase coke, synthetic coke, leonardite, anthracite, lignite coal, bituminous coal, natural coal mineral powder, and a combination thereof; (b) rapidly depressurizing said supercritical fluid at a fluid release rate sufficient for effecting exfoliation and separation of said coke or coal powder to produce isolated graphene sheets, which are dispersed in a liquid medium to produce a graphene suspension; and (c) shaping and drying said graphene suspension to form said supercapacitor electrode that is porous and has a specific surface area greater than 200 m 2 /g.

2 . The process of claim 1 wherein said particles of said coke or coal powder have never been previously intercalated or oxidized prior to step (a).

3 . The process of claim 1 wherein said supercapacitor electrode is in a paper sheet, porous film, porous filament, porous rod, or porous tube form.

4 . The process of claim 1 , wherein said supercritical fluid comprises a fluid selected from carbon dioxide, water, hydrogen peroxide (H 2 O 2 ), methanol, ethanol, acetone, methane, ethane, propane, ethylene, propylene, nitrous oxide (N 2 O), ozone, sulfonic group (SO 3 ), or a combination thereof.

5 . The process of claim 1 , wherein said step (a) is conducted under the influence of ultrasonic waves.

6 . The process of claim 1 , further comprising a procedure of essentially repeating step (a) and step (b) that includes (i) subjecting said isolated graphene sheets to a supercritical fluid at a second temperature and a second pressure for a second period of time in a pressure vessel and then (ii) rapidly depressurizing said fluid at a fluid release rate sufficient for effecting further exfoliation and separation of graphene sheets.

7 . The process of claim 1 , wherein said supercritical fluid contains a surfactant or dispersing agent dissolved therein.

8 . The process of claim 1 , wherein said pressure vessel further contains a surfactant or dispersing agent selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, silicone surfactants, fluoro-surfactants, polymeric surfactants, sodium hexametaphosphate, sodium lignosulphonate, poly (sodium 4-styrene sulfonate), sodium dodecylsulfate, sodium sulfate, sodium phosphate, sodium sulfonate, and combinations thereof.

9 . The process of claim 1 , wherein said pressure vessel further contains a surfactant or dispersing agent selected from melamine, ammonium sulfate, sodium dodecyl sulfate, sodium (ethylenediamine), tetraalkyammonium, ammonia, carbamide, hexamethylenetetramine, organic amine, pyrene, 1-pyrenecarboxylic acid, 1-pyrenebutyric acid, 1-pyrenamine, poly(sodium-4-styrene sulfonate), or a combination thereof.

10 . The process of claim 1 , wherein said supercritical fluid contains therein an organic solvent, a monomer, an oligomer, a polymer solution, or a combination thereof.

11 . The process of claim 1 wherein said supercritical fluid contains a coating agent dissolved therein.

12 . The process of claim 11 , wherein said coating agent comprises a monomer, a prepolymer or oligomer, a polymer, a resin, a curing agent, or a combination thereof.

13 . The process of claim 1 wherein said liquid medium comprises water, an organic solvent, alcohol, a monomer, an oligomer, or a combination thereof.

14 . The process of claim 1 wherein said liquid medium further comprises a monomer or an oligomer dispersed in said liquid medium and said step (c) is followed by polymerization of said monomer or oligomer to form a polymer.

15 . The process of claim 14 , further comprising a step of thermally converting said polymer into carbon or graphite that acts as a binder to bond said isolated graphene sheets together to form said supercapacitor electrode that has a specific surface area greater than 500 m 2 /g.

16 . The process of claim 15 , wherein said specific surface area is greater than 1,000 m 2 /g.

17 . The process of claim 16 , wherein said specific surface area is greater than 2,000 m 2 /g.

18 . The process of claim 1 wherein said liquid medium further comprises a polymer dissolved or dispersed in said liquid medium and said isolated graphene sheets are mixed with said polymer to form a composite composition.

19 . The process of claim 18 , further comprising a step of thermally converting said polymer into carbon or graphite that acts as a binder to bond said isolated graphene sheets together to form said supercapacitor electrode that has a specific surface area greater than 500 m 2 /g.

20 . The process of claim 19 , wherein said specific surface area is greater than 1,000 m 2 /g

21 . The process of claim 1 , wherein a desired amount of a foaming agent is added into said graphene suspension and said step (c) includes depositing said graphene suspension onto a surface of a solid substrate to form a wet graphene film under the influence of a shear stress or compressive stress to align said graphene sheets parallel to said substrate surface, and wherein said wet film is dried and heated to form a porous dry graphene film.

22 . The process of claim 1 , wherein a desired amount of a foaming agent is added into said graphene suspension and said step (c) includes shaping the graphene suspension using a procedure of casting, coating, spraying, printing, extrusion, fiber spinning, or a combination thereof.

23 . The process of claim 21 , wherein said wet graphene film or dry graphene film is subjected to a heat treatment at a temperature from 100° C. to 3,200° C.

24 . The process of claim 1 , wherein said step (b) comprises discharging said isolated graphene sheets, during or after said depressurizing, into said liquid medium.

25 . The process of claim 1 , wherein said step of shaping and drying said graphene suspension comprises dispensing said suspension onto a surface or two surfaces of a current collector to form said electrode in a film form having a thickness from 1 μm to 1,000 μm.

26 . The process of claim 1 , wherein said step of shaping and drying said graphene suspension comprises dispensing and heat treating said suspension to form a layer of graphene foam having a thickness from 1 μm to 1,000 μm.

27 . The process of claim 1 , wherein said step of shaping and drying said graphene suspension comprises freeze-drying said suspension to form a graphene foam electrode.

28 . The process of claim 1 , wherein said electrode has an active material mass loading higher than 10 mg/cm 2 .

29 . The process of claim 1 , wherein said electrode has an active material mass loading higher than 20 mg/cm 2 .

Assignees

• Nanotek Instruments Inc

Inventors

• Zhamu Aruna
• Jang Bor Z

Classifications

• C01B2204/22

  Electronic properties · CPC title

• C01B2204/04

  Specific amount of layers or specific thickness · CPC title

• C01B32/192

  starting from graphitic oxides · CPC title

• C01B2204/32

  Size or surface area · CPC title

• C01B2204/02

  Single layer graphene · CPC title