Large-grain graphene thin film current collector and secondary batteries containing same
View Patent ↗A unitary graphene-based current collector in a battery or capacitor. The current collector is or contains a unitary graphene layer that is composed of closely packed and chemically bonded parallel graphene planes having an inter-graphene plane spacing of 0.335 to 0.40 nm and an oxygen content less than 5% by weight (more typically 0.001% to 1%), an average grain size larger than 5 μm (more typically >100 μm; some as large as >cm), a physical density higher than 1.8 g/cm 3 , and is obtained from heat-treating a graphene oxide gel at a temperature higher than 100° C. (typically and preferably from 1,000 to 3,000° C.). Such an integrated or unitary graphene entity is compatible with essentially all electrolytes commonly used in batteries and supercapacitors.
1. A unitary graphene layer-based current collector in a battery or capacitor, said current collector being a unitary graphene layer containing closely packed and chemically bonded parallel graphene planes having an inter-graphene plane spacing of 0.335 to 0.40 nm and an oxygen content less than 5% by weight, an average grain size larger than 5 μm, a physical density higher than 1.8 g/cm 3 , and a tensile strength greater than 40 MPa, and is obtained from heat-treating a graphene oxide gel at a temperature higher than 100° C., wherein said current collector is not an electrode active layer.
2. The current collector of claim 1 , wherein said average grain size is larger than 10 μm.
3. The current collector of claim 1 , wherein said average grain size is larger than 20 μm.
4. The current collector of claim 1 , wherein said average grain size is larger than 100 μm.
5. The current collector of claim 1 , wherein said average grain size is larger than 200 μm.
6. The current collector of claim 1 , wherein the unitary graphene layer has an oxygen content from 0.001% to 2% by weight.
7. The current collector of claim 1 , wherein said heat treatment temperature contains a temperature in the range of 500° C.-1,250° C. and the unitary graphene layer has an oxygen content less than 1%, an inter-graphene spacing less than 0.345 nm, and an electrical conductivity no less than 3,000 S/cm.
8. The current collector of claim 1 , wherein said heat treatment temperature contains a temperature in the range of 1,250° C.-2,000° C. and the unitary graphene layer has an oxygen content less than 0.01%, an inter-graphene spacing less than 0.337 nm, and an electrical conductivity no less than 5,000 S/cm.
9. The current collector of claim 1 , wherein said heat treatment temperature contains a temperature greater than 2,000° C. and the unitary graphene layer has an oxygen content no greater than 0.001%, an inter-graphene spacing less than 0.336 nm, a mosaic spread value no greater than 0.7, and an electrical conductivity no less than 8,000 S/cm.
10. The current collector of claim 1 , wherein said heat treatment temperature contains a temperature no less than 2,500° C. and the unitary graphene layer has an inter-graphene spacing less than 0.336 nm, a mosaic spread value no greater than 0.4, and an electrical conductivity greater than 10,000 S/cm.
11. The current collector of claim 1 , wherein the unitary graphene layer exhibits an inter-graphene spacing less than 0.337 nm and a mosaic spread value less than 1.0.
12. The current collector of claim 1 , wherein the unitary graphene layer exhibits a degree of graphitization no less than 40% and/or a mosaic spread value less than 0.7.
13. The current collector of claim 1 , wherein the unitary graphene layer exhibits a degree of graphitization no less than 80% and/or a mosaic spread value no greater than 0.4.
14. The current collector of claim 1 , wherein said unitary graphene layer contains chemically bonded graphene molecules or chemically merged graphene planes that are parallel to one another.
15. The current collector of claim 1 , wherein said unitary graphene layer contains no complete grain boundary therein, is a graphene single crystal, or a poly-crystal graphene structure with graphene molecules being oriented along a preferred direction.
16. The current collector of claim 1 , wherein said graphene oxide gel is obtained from a graphitic material having a maximum original graphite grain size and said unitary graphene layer is a poly-crystal graphene structure having a grain size larger than said maximum original grain size.
17. The current collector of claim 1 , wherein said graphene oxide gel is produced from particles of a natural graphite or artificial graphite composed of graphite crystallites having an initial length L a in the crystallographic a-axis direction, an initial width L b in the b-axis direction, and a thickness L c in the c-axis direction, and the unitary graphene layer has a length or width greater than the initial L a and L b of the graphite crystallites.
18. The current collector of claim 1 , wherein said graphene oxide gel is produced from particles of a natural graphite or artificial graphite composed of graphite crystallites having an initial length L a in the crystallographic a-axis direction, an initial width L b in the b-axis direction, and a thickness L c in the c-axis direction and the unitary graphene layer has a length or width at least greater than twice the initial L a or twice the initial L b of the graphite crystallites.
19. The current collector of claim 1 , wherein the chemically bonded parallel graphene planes contain a combination of sp 2 and sp a electronic configurations.
20. The current collector of claim 1 , wherein said unitary graphene layer has a length or width no less than 100 μm.
21. The current collector of claim 1 , wherein said unitary graphene layer has a length or width no less than 1 mm.
22. The current collector of claim 1 , wherein said unitary graphene layer has a length or width no less than 1 cm.
23. The current collector of claim 1 , wherein said unitary graphene layer has a thickness greater than 100 nm.
24. The current collector of claim 1 , wherein said unitary graphene layer has a thickness greater than 500 nm.
25. The current collector of claim 1 , wherein said unitary graphene layer has a thickness greater than 1 μm.
26. The current collector of claim 1 , wherein said unitary graphene layer has a thickness from 1 μm to 10 μm.
27. The current collector of claim 1 , wherein said unitary graphene layer has a thickness from 1 μm to 20 μm.
28. The current collector of claim 1 , further comprising an electrically conductive reinforcement material selected from carbon nano-tube, carbon nano-fiber, discrete graphene platelet, expanded graphite platelet, conductive polymer fiber, metal fiber, micron-scaled carbon fiber, or a combination thereof to form a reinforced graphene matrix composite.
29. The current collector of claim 1 , having a physical density greater than 1.9 g/cm3, and/or a tensile strength greater than 40 MPa.
30. The current collector of claim 1 , having a physical density greater than 2.0 g/cm3, and/or a tensile strength greater than 60 MPa.
31. The current collector of claim 1 , having a physical density greater than 2.1 g/cm 3 , and/or a tensile strength greater than 80 MPa.
32. A rechargeable lithium battery or lithium-ion battery containing the current collector of claim 1 as an anode current collector or a cathode current collector.
33. A rechargeable lithium battery containing the current collector of claim 1 as an anode current collector or a cathode current collector, which lithium battery is a lithium-sulfur cell, a lithium-selenium cell, a lithium sulfur/selenium cell, a lithium-air cell, a lithium-graphene cell, or a lithium-carbon cell.
34. A capacitor containing the current collector of claim 1 as an anode current collector or a cathode current collector, which capacitor is a symmetric ultracapacitor, an asymmetric ultracapacitor cell, a hybrid supercapacitor-battery cell, or a lithium-ion capacitor cell.