Energy storage devices

• US 9,412,998 B2
• Filed: 12/21/2012
• Issued: 08/09/2016
• Est. Priority Date: 02/25/2009
• Status: Active Grant

• Current Assignee: Kansas State University Research Foundation, CF Traverse LLC (SoftBank Group Corp.)
• Original Assignee: Traverse Technologies Corp. (Marathon Patent Group, Inc.)
• Inventors: Rojeski, Ronald A., Klankowski, Steven, Li, Jun
• Primary Examiner(s): GATEWOOD, DANIEL S
• Application Number:
  US13/725,969
• Publication Number:
  US 20130177814A1
• Time in Patent Office: 1,327 Days
• Field of Search: None
• US Class Current: 1/1
• 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: B82Y 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: H01G 9/042 characterised by the material H01G11/22 takes precedence
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/139 Processes of manufacture
• CPC Class Codes: H01M 4/70 characterised by shape or form
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y10S 977/734 Fullerenes, i.e. graphene-based structures, such as nanohorns, nanococoons, nanoscrolls or fullerene-like structures, e.g. WS2 or MoS2 chalcogenide nanotubes, planar C3N4, etc.

Abstract

A novel hybrid lithium-ion anode material based on coaxially coated Si shells on vertically aligned carbon nanofiber (CNF) arrays. The unique cup-stacking graphitic microstructure makes the bare vertically aligned CNF array an effective Li⁺ intercalation medium. Highly reversible Li⁺ intercalation and extraction were observed at high power rates. More importantly, the highly conductive and mechanically stable CNF core optionally supports a coaxially coated amorphous Si shell which has much higher theoretical specific capacity by forming fully lithiated alloy. The broken graphitic edges at the CNF sidewall ensure good electrical connection with the Si shell during charge/discharge processes.

Claims

1. An energy storage system comprising:

a conductive substrate;

a plurality of carbon nanofibers on the substrate, the carbon nanofibers including a plurality of multi-walled carbon nanotubes;

an electrolyte including one or more charge carriers, wherein the carbon nanofibers include a stacked-cone structure; and

a layer of intercalation material on the carbon nanofibers, the layer of intercalation material having a structure resulting from the stacked-cone structure.

31. The system of claim 1, wherein the structure is a feather-like structure.

40. The system of claim 1, wherein the carbon nanotubes are configured such that ion intercalation can occur into the carbon nanotubes through sidewalls of the carbon nanofibers.

2. An energy storage system comprising:

a conductive substrate;

a plurality of carbon nanofibers on the substrate, the carbon nanofibers including a plurality of multi-walled carbon nanotubes;

an electrolyte including one or more charge carriers; and

a layer of intercalation material on the carbon nanofibers, the layer of intercalation material comprising structures of silicon coated by surface electrolyte interphase.

3. The system of claim 2, wherein the intercalation material has a nominal thickness of between 0.01 and 5 μ

m.

4. The system of claim 3, wherein the layer of intercalation material includes nanofiber/intercalation material complexes, some of the nanofiber/intercalation material complexes including one nanofiber and some of the nanofiber/intercalation material complexes including two nanofibers.

5. The system of claim 2, wherein the silicon has a nominal thickness of between approximately 0.01 μ

m and 40 μ

m.

6. The system of claim 2, wherein the carbon nanofibers are between 1.0 and 200 μ

m in length.

7. The system of claim 6, wherein the silicon covers less than 25% of the carbon nanofibers.

17. The system of claim 2, wherein the carbon nanofibers each include graphitic edges along sides of the carbon nanofibers.

18. The system of claim 2, wherein the carbon nanofibers are vertically aligned and grown on the substrate.

19. The system of claim 2, wherein the intercalation material being disposed to cover less than 25% of the carbon nanofibers.

20. The system of claim 2, further comprising an overlayer partially or fully encapsulating the intercalation material, the intercalation material including silicon and the overlayer including SiO₂.

21. The system of claim 20, wherein the intercalation material is disposed to cover less than 25% of the carbon nanofibers.

29. The system of claim 2, wherein the carbon nanofibers are entangled.

30. The system of claim 2, wherein the surface electrolyte interphase has a feather-like structure.

32. The system of claim 2, wherein the structures are feather-like structures.

33. The system of claim 2, wherein the structures result from a structure of each of the multi-walled carbon nanotubes.

8. An energy storage system comprising:

a conductive substrate;

a plurality of connected carbon nanofibers on the substrate; and

a layer of intercalation material disposed on the plurality of carbon nanofibers and configured to have a lithium ion storage capacity of between approximately 750 and 4,000 mAh per gram of intercalation material at a charging rate of 10 C.

9. The system of claim 8, wherein a lithium ion storage capacity of between approximately 1,500 and 4,000 mAh per gram of intercalation material is achieved at a charging rate of 1 C and at a charging rate of 10 C.

10. The system of claim 8, wherein the lithium ion storage capacity of between approximately 750 and 4,000 mAh per gram of intercalation material is achieved at a charging rate of 1 C and at a charging rate of 10 C.

11. The system of claim 8, wherein a lithium ion storage capacity of between approximately 1,500 and 4,000 mAh per gram of intercalation material is achieved after 100 charge-discharge cycles.

12. The system of claim 8, wherein a lithium ion storage capacity of between 2,000 and 4,000 mAh per gram of silicon is achieved at a charging rate of C/2 and at a charging rate of 10 C.

13. The system of claim 12, wherein the intercalation material includes silicon.

22. The system of claim 8, wherein the carbon nanofibers include multi-walled carbon nanotubes.

23. The system of claim 8, wherein the carbon nanofibers are connected by a part of the intercalation material that envelops more than one carbon nanofiber.

34. The system of claim 8, wherein the intercalation material includes silicon particles and is disposed to cover less than 25% of the carbon nanotubes.

14. An energy storage system comprising:

a conductive substrate;

a plurality of carbon nanofibers on the substrate; and

a layer of intercalation material disposed on the plurality of carbon nanofibers and configured such that an ion storage capacity of the intercalation material is approximately the same at charging rates of 1 C and 3 C.

15. The system of claim 14, wherein the ion storage capacity increases as the charging rate is increased from 3 C to 10 C.

16. The system of claim 14, wherein the ion storage capacity changes by less than 25% between charging rates of 0.3 C and 3 C.

24. An energy storage system comprising:

a conductive substrate;

a plurality of carbon nanofibers on the substrate, the carbon nanofibers including graphitic edges along a sidewall of the carbon nanofibers; and

a layer of intercalation material disposed on the plurality of carbon nanofibers and including silicon, wherein a structure of the intercalation material is responsive to the graphitic edges.

25. The system of claim 24, wherein the carbon nanofibers are grown on the conductive substrate.

26. The system of claim 24, wherein the carbon nanofibers are configured for Li⁺ intercalation between the graphitic edges.

27. The system of claim 24, wherein the intercalation material is configured such that a volume change in the intercalation material is dominated by radial expansion, perpendicular to axes of the carbon nanofibers, during charge carrier intercalation.

28. The system of claim 24, further comprising an overlayer partially or fully encapsulating the intercalation material, the intercalation material including silicon and the overlayer including SiO₂.

35. The system of claim 28, wherein the intercalation material is disposed to cover less than 25% of the carbon nanofibers.

36. A system comprising:

an electrode disposed in a first region of electrolyte and including

a substrate,

a plurality of support filaments, and

an ion absorbing material attached to the support filaments and including silicon, the ion adsorbing material covering less than 25% of the support filaments;

a separator configured to separate the first region and a second region of electrolyte; and

a cathode disposed in the second region of electrolyte, the cathode, anode and separator configured to operate as a rechargeable battery.

37. The system of claim 36, wherein the support filaments comprise a carbon nano-tube (CNT), a carbon nano-fiber (CNF), or a nano-wire (NW).

38. The system of claim 36, wherein the ion absorbing material is attached to the support filaments by a binder.

39. the system of claim 36, wherein the ion absorbing material includes silicon particles.