Graphene materials having randomly distributed two-dimensional structural defects
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.
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 two-dimensional defect pores in the plane of the graphene sheet, the defect pores comprising in-plane carbon vacancies in the graphene structure, and further wherein at least a portion of the plurality of graphene sheets form a crystalline graphite structure.
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 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.
5. The material of claim 4 , wherein the electrochemically active material is silicon.
6. The material of claim 5 , wherein the silicon is in the form of silicon nanoparticles dispersed between the graphene sheets in the disordered portions of the vertical stack.
7. 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 in which at least a portion of the plurality of graphene sheets form a crystalline graphite structure, and further wherein graphene sheets within the vertical stack comprise randomly-distributed two-dimensional defect pores in the plane of the graphene sheet, the defect pores comprising in-plane carbon vacancies in the graphene structure.
8. The lithium ion battery of claim 7 , wherein the average diameter of the defect pores is in the range from about 1 nm to about 100 nm.
9. The lithium ion battery of claim 7 , 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.
10. The lithium ion battery of claim 9 , wherein the electrochemically active material comprises nanoparticles dispersed between the graphene sheets in the disordered portions of the vertical stack.
11. The lithium ion battery of claim 10 , wherein the nanoparticles are silicon nanoparticles.
12. The lithium ion battery of claim 9 , 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.
13. The material of claim 1 , wherein the defect pores include defect pores having diameters in the range from 10 to 20 nm.
14. The material of claim 1 , wherein the defect pores include defect pores having diameters greater than 100 nm.
15. The material of claim 1 , wherein the defect pores include defect pores having diameters in the range from 20 nm to 100 nm.
16. The material of claim 1 , comprising eleven graphene sheets disposed in the vertical stack.
17. The lithium ion battery of claim 7 , wherein the defect pores include defect pores having diameters in the range from 10 to 20 nm.
18. The lithium ion battery of claim 7 , wherein the defect pores include defect pores having diameters greater than 100 nm.
19. The lithium ion battery of claim 7 , wherein the defect pores include defect pores having diameters in the range from 20 nm to 100 nm.
20. The lithium ion battery of claim 19 , wherein the diameters are measured using field emission transmission electron microscopy.
21. The lithium ion battery of claim 7 , wherein the defect pores enhance the diffusion of lithium ions into the interior of the vertical stack of graphene sheets relative to that of the vertical stack of graphene sheets in the absence of the defect pores.