GRAPHENE MATERIALS HAVING RANDOMLY DISTRIBUTED TWO-DIMENSIONAL STRUCTURAL DEFECTS

• US 20120288750A1
• Filed: 05/12/2011
• Published: 11/15/2012
• Est. Priority Date: 05/12/2011
• Status: Active Grant

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Kung, Harold H., Kung, Mayfair C., Zhao, Xin, Hayner, Cary M.
• Granted Patent: US 8,551,650 B2
• Time in Patent Office: Days
• US Class Current: 429/188
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 32/192 starting from graphitic oxides
• CPC Class Codes: C01B 32/23 Oxidation
• CPC Class Codes: H01B 1/04 mainly consisting of carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/625 Carbon or graphite
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Graphene-based storage materials for high-power battery applications are provided. The storage materials are composed of vertical stacks of graphene sheets and have reduced resistance for Li ion transport. This reduced resistance is achieved by incorporating a random distribution of structural defects into the stacked graphene sheets, whereby the structural defects facilitate the diffusion of Li ions into the interior of the storage materials.

Claims

1. A graphene-based material comprising a plurality of graphene sheets disposed in a vertical stack, wherein graphene sheets within the vertical stack comprise randomly-distributed defect pores formed by in-plane carbon vacancies.

2. The material of claim 1, wherein the average diameter of the defect pores is in the range from about 1 nm to about 100 nm.

3. The material of claim 1, wherein the average diameter of the defect pores is no greater than 30 nm.

4. The material of claim 1, wherein the average density of defect pores in the graphene sheets as measured by the ratio of the average separation distance between adjacent pores to the average pore diameter, is at least 3.

5. The material of claim 1, wherein the average density of defect pores in the graphene sheets as measured by the ratio of the average separation distance between adjacent pores to the average pore diameter, is at least 100.

6. The material of claim 1, wherein the graphene sheets are part of a structure comprising a continuous network of graphitic regions comprising crystalline portions of the vertical stack of graphene sheets, and further wherein the continuous network of graphitic regions is integrated with a composite comprising:

(a) disordered portions of the vertical stack of graphene sheets; and

(b) an electrochemically active material in contact with the graphene sheets in the disordered portions of the vertical stack.

7. The material of claim 6, wherein the electrochemically active material is silicon.

8. The material of claim 7, wherein the silicon is in the form of silicon nanoparticles dispersed between the graphene sheets in the disordered portions of the vertical stack.

9. A lithium ion battery comprising a cathode, an anode and a non-aqueous electrolyte comprising a lithium salt disposed between the cathode and the anode, wherein the anode comprises a plurality of graphene sheets disposed in a vertical stack, and further wherein graphene sheets within the vertical stack comprise randomly-distributed defect pores formed by in-plane carbon vacancies.

10. The lithium ion battery of claim 9, wherein the average diameter of the defect pores is in the range from about 1 nm to about 100 nm.

11. The lithium ion battery of claim 9, wherein the average density of defect pores in the graphene sheets as measured by the ratio of the average separation distance between adjacent pores to the average pore diameter, is at least 3.

12. The lithium ion battery of claim 9, wherein the graphene sheets are part of a structure comprising a continuous network of graphitic regions comprising crystalline portions of the vertical stack of graphene sheets, and further wherein the continuous network of graphitic regions is integrated with a composite comprising:

(a) disordered portions of the vertical stack of graphene sheets; and

(b) an electrochemically active material in contact with the graphene sheets in the disordered portions of the vertical stack.

13. The lithium ion battery of claim 12, wherein the electrochemically active material comprises nanoparticles dispersed between the graphene sheets in the disordered portions of the vertical stack.

14. The lithium ion battery of claim 13, wherein the nanoparticles are silicon nanoparticles.

15. The lithium ion battery of claim 12, wherein the battery can deliver a power density of at least 2 kW/kg and an energy density of at least 300 Wh/kg for a period of at least 8 minutes.

16. A method for making an electrode material, the method comprising:

(a) exposing a suspension of exfoliated, oxidized graphene sheets to an acid at an acid concentration high enough, and an exposure time long enough, to generate defect pores formed from carbon vacancies in the oxidized graphene sheets;

(b) removing the oxidized graphene sheets from the suspension;

(c) reducing the oxidized graphene sheets to form a vertical stack of graphene sheets having a random distribution of defect pores distributed therein.

17. The method of claim 16, wherein the average diameter of the defect pores is in the range from about 1 nm to about 100 nm.

18. The method of claim 16, wherein the average density of defect pores in the graphene sheets as measured by the ratio of the average separation distance between adjacent pores to the average pore diameter, is at least 3.

19. The method of claim 16, further comprising mixing the oxidized graphene sheets in suspension with electrochemically active nanoparticles, such that the nanoparticles are dispersed between the graphene sheets, whereby when the oxidized graphene sheets are removed from the suspension and reduced, the resulting material comprises a network of graphitic regions comprising crystalline portions of the vertical stack of graphene sheets integrated with a composite comprising disordered portions of the vertical stack of graphene sheets and nanoparticles of the electrochemically active material dispersed between the graphene sheets in the disordered portions of the vertical stack, the graphene sheets having a random distribution of defect pores distributed therein.

20. The method of claim 19, wherein the nanoparticles are silicon nanoparticles.