Cellular graphene films

Patent metadata

Field	Value
Publication number	US-2017178824-A1
Application number	US-201615382871-A
Country	US
Kind code	A1
Filing date	Dec 19, 2016
Priority date	Dec 22, 2015
Publication date	Jun 22, 2017
Grant date	—

Abstract

The present disclosure provides supercapacitors that may avoid the shortcomings of current energy storage technology. Provided herein are electrochemical systems, comprising three dimensional porous reduced graphene oxide film electrodes. Prototype supercapacitors disclosed herein may exhibit improved performance compared to commercial supercapacitors. Additionally, the present disclosure provides a simple, yet versatile technique for the fabrication of supercapacitors through the direct preparation of three dimensional porous reduced graphene oxide films by filtration and freeze casting.

First claim

What is claimed is:

1 . A reduced graphene oxide film comprising a three-dimensional hierarchy of pores and having an active density of up to about 0.5 g/cm 3 .

2 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has an areal mass loading of at least about 0.1 mg/cm 2 .

3 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a tensile strength of at least about 9 MPa.

4 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a conductivity of at least about 1,000 S/m.

5 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a gravimetric energy density of at least about 4 Wh/kg.

6 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a gravimetric power density of at least about 25 kW/kg.

7 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a gravimetric capacitance, in a current density of 1 A/g, of at least about 90 F/g.

8 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has a capacitive retention, after about 1000 cycles of charging, of at least about 50%.

9 . The reduced graphene oxide film of claim 1 , wherein the reduced graphene oxide film has an areal capacitance of at least about 25 mF/cm 2 .

10 . A supercapacitor device comprising:
(a) two electrodes, wherein at least one electrode comprises a reduced graphene oxide film comprising a three-dimensional hierarchy of pores; (b) an electrolyte; and (c) an separator disposed between the first electrode and the second electrode.

11 . The supercapacitor of claim 10 , wherein the at least one electrode comprising a reduced graphene oxide film has a thickness of from about 6 μm to about 60 μm.

12 . The supercapacitor of claim 10 , wherein the electrolyte comprises a strong acid comprising perchloric acid, hydroiodic acid, hydrobromic acid, hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, or any combination thereof.

13 . The supercapacitor of claim 10 , wherein the separator comprises a polymer comprising neoprene, nylon, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyacrylonitrile, polyvinyl butyral, silicone, or any combination thereof.

14 . The supercapacitor of claim 10 , provided that the supercapacitor has a volumetric energy density of at least about 0.1 Wh/L.

15 . The supercapacitor of claim 10 , provided that the supercapacitor has a volumetric power density of at least about 3 kW/L.

16 . A method of fabricating a graphene oxide film, comprising:
(a) suspending a graphene oxide in a first solvent to form a graphene oxide suspension; (b) dispersing the graphene oxide suspension in a second solvent to form a graphene oxide dispersion; (c) reducing the graphene oxide dispersion; (d) filtering the graphene oxide dispersion through a membrane to form a graphene oxide film on the membrane; and (e) freeze-casting the graphene oxide film on the membrane.

17 . The method of claim 16 , wherein a concentration of the graphene oxide in the first solvent is from about 1 mg/mL to about 6 mg/mL.

18 . The method of claim 16 , wherein the second solvent comprises a weak acid comprising formic acid, citric acid, acetic acid, ascorbic acid, malic acid, tartaric acid, propionic acid, butyric acid, valeric acid, caprioc acid, oxalic acid, benzoic acid, carbonic acid, or any combination thereof.

19 . The method of claim 16 , wherein the graphine oxide dispersion comprises a volume of the graphene oxide suspension of from about 0.5 mL to about 10 mL, and a mass of the second solvent of from about 3 mg to about 70 mg.

20 . The method of claim 16 , wherein (c) comprises heating the graphene oxide dispersion at a temperature of from about 25° C. to about 100° C.

21 . The method of claim 16 , wherein (c) comprises heating the graphene oxide dispersion over a period of from about 1 minute to about 100 minutes.

22 . The method of claim 16 , wherein the membrane has a pore size of from about 0.1 μm to about 0.5 μm.

23 . The method of claim 16 , wherein (e) comprises:
(f) freezing the graphene oxide film on the membrane; (g) thawing the graphene oxide film on the membrane; (h) heating the graphene oxide film on the membrane; and (i) immersing the graphene oxide film on the membrane in a third solvent.

24 . The method of claim 23 , wherein the graphene oxide film is frozen on the membrane for a period of time of at least about 15 minutes.

25 . The method of claim 23 , wherein the heating of the graphene oxide film on the membrane occurs at a temperature of from about 50° C. to about 200° C.

26 . The method of claim 16 , provided that the graphene oxide film has a thickness of from about 6 μm to about 60 μm.

Assignees

• Univ California

Inventors

• Kaner Richard Barry
• Shao Yuanlong

Classifications

• H01G11/32 Primary

  Carbon-based · CPC title

• H01G11/36

  Nanostructures, e.g. nanofibres, nanotubes or fullerenes · CPC title

• C01P2006/10

  Solid density · CPC title

• H01G11/60

  characterised by the solvent · CPC title

• C01P2006/40

  Electric properties · CPC title