Energy Storage Devices

• US 20130177814A1
• Filed: 12/21/2012
• Published: 07/11/2013
• 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., Li, Jun, Klankowski, Steven
• Granted Patent: US 9,412,998 B2
• Time in Patent Office: Days
• US Class Current: 429/231.8
• 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 vertically aligned carbon nanofibers grown on the substrate, the carbon nanofibers each including a plurality multi-walled carbon nanotubes; and

an electrolyte including one or more charge carriers.

2. The system of claim 1, wherein the carbon nanotubes are dispose such that ion intercalation can occur between walls of the nanotubes through the sidewalls of the carbon nanofibers.

3. The system of claim 1, wherein the carbon nanofibers include a stacked-cone structure.

4. The system of claim 3, further comprising a layer of intercalation material on the carbon nanofibers, the layer of intercalation material having a feather-like structure resulting from the stacked-cone structure.

5. The system of claim 1, further comprising a layer of intercalation material on the carbon nanofibers, the layer of intercalation material comprising feather-like structures of silicon filled with surface electrolyte interphase.

6. The system of claim 1, further comprising a layer of intercalation material on the carbon nanofibers, the intercalation material having a nominal thickness of between 0.1 and 25 μ

m.

7. The system of claim 6, 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.

8. The system of claim 1, further comprising a layer of intercalation material on the carbon nanofibers, the silicon having a nominal thickness of between approximately 1.0 μ

m and 40 μ

m.

9. The system of claim 1, wherein the carbon nanofibers are between 3.0 and 200 μ

m in length.

10. The system of claim 9, wherein the intercalation material includes silicon.

11. An energy storage system comprising:

a conductive substrate;

a plurality of vertically aligned carbon nanofibers grown on the substrate; and

a layer of intercalation material disposed on the plurality of vertically aligned carbon nanofibers and configured to have a lithium ion storage capacity of between approximately 1,500 and 4,000 mAh per gram of intercalation material.

12. The system of claim 11, wherein the lithium ion storage capacity of between approximately 1,500 and 4,000 mAh per gram of intercalation material is achieved at a charging rate between 1 C and 10 C.

13. The system of claim 11, 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 between 1 C and 10 C.

14. The system of claim 11, wherein the 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.

15. The system of claim 11, wherein the lithium ion storage capacity of between approximately 1,500 and 4,000 mAh per gram of intercalation material is between 2,000 and 4,000 mAh per gram of silicon at a charging rate between C/2 and 10 C.

16. The system of claim 15, wherein the intercalation material includes silicon.

17. An energy storage system comprising:

a conductive substrate;

a plurality of vertically aligned carbon nanofibers grown on the substrate; and

a layer of intercalation material disposed on the plurality of vertically aligned 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.

18. The system of claim 17, wherein the ion storage capacity increases as the charging rate is increased from 3 C to 10 C.

19. The system of claim 17, wherein the ion storage capacity changes by less than 25% between charging rates of 0.3 C and 3 C.

20. A method of producing an energy storage device, the method comprising:

providing a substrate;

growing carbon nanofibers on the substrate, the carbon nonofibers having a stacked-cone structure; and

applying intercalation material to the carbon nanofibers, the intercalation material being configured for intercalation of charge carriers.

21. The method of claim 20, wherein the applied intercalation material produces a feather-like structure.

22. The method of claim 20, further comprising providing nucleation sites for growing the carbon nanofibers, a density of the nucleation sites being selected to achieve an average nearest neighbor separation distance of the carbon nanofibers of between 75 and 400 nanometers.

23. The method of claim 20, further comprising conditioning the energy storage device at such that it has a lithium ion storage capacity of between approximately 750 and 4,000 mAh per gram of silicon at a charge rate of at least 1 C.

24. The method of claim 20, further comprising conditioning the energy storage device such that the intercalation material and an electrolyte interact to form a surface electrolyte interphase, the surface electrolyte interphase being formed between feather-like structures of the intercalation material.

25. The system of claim 24, wherein the intercalation material includes silicon.