Production of Graphene-Based Supercapacitor Electrode from Coke or Coal Using Direct Ultrasonication

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) dispersing particles of said coke or coal powder in a liquid medium containing therein an optional surfactant or dispersing agent to produce a suspension or slurry, 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) exposing said suspension or slurry to ultrasonication at an energy level for a sufficient length of time to produce a graphene suspension containing isolated graphene sheets dispersed in said liquid medium; 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, filament, rod, or tube form.

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

5 . The process of claim 1 wherein said liquid medium further comprises a monomer or an oligomer dispersed in said liquid medium and, in said step (b), said ultrasonication also induces polymerization of said monomer or oligomer to form a polymer.

6 . The process of claim 5 , 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.

7 . The process of claim 6 , wherein said specific surface area is greater than 1,000 m 2 /g.

8 . The process of claim 6 , wherein said specific surface area is greater than 2,000 m 2 /g.

9 . 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.

10 . The process of claim 9 , 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.

11 . The process of claim 10 , wherein said specific surface area is greater than 1,000 m 2 /g

12 . The process of claim 1 wherein said surfactant or dispersing agent is 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.

13 . The process of claim 1 wherein said surfactant or dispersing agent is 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.

14 . 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 to form a porous dry graphene film.

15 . 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.

16 . The process of claim 14 , 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.

17 . 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.

18 . The process of claim 5 , 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.

19 . The process of claim 9 , 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.

20 . 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.

21 . 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.

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

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