Method of making silicon anode material for rechargeable cells

• US 9,553,304 B2
• Filed: 01/15/2015
• Issued: 01/24/2017
• Est. Priority Date: 05/07/2009
• Status: Active Grant

• Current Assignee: Nexeon Limited
• Original Assignee: Nexeon Limited
• Inventors: Rayner, Philip John
• Primary Examiner(s): SIDDIQUEE, MUHAMMAD S
• Application Number:
  US14/597,875
• Publication Number:
  US 20150125754A1
• Time in Patent Office: 740 Days
• US Class Current: 1/1
• CPC Class Codes: C22C 21/02 with silicon as the next major constituent
• CPC Class Codes: C22C 21/04 Modified aluminium-silicon alloys
• 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 4/0492 Chemical attack of the support material
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/38 of elements or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/583 Carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 428/24149 Honeycomb-like
• CPC Class Codes: Y10T 428/298 Physical dimension
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

There is provided a method of forming silicon anode material for rechargeable cells. The method includes providing a metal matrix, comprising no more than 30 wt % silicon, including silicon structures dispersed therein. The method further includes at least partially etching the metal matrix to at least partially isolate the silicon structures.

Claims

1. An electroactive material comprising silicon structures, wherein

the silicon structures have been at least partially isolated from a solidified aluminum-based metal-silicon alloy comprising less than 30 wt % silicon, the solidified aluminum-based metal-silicon alloy comprising an aluminum-based metal and the silicon structures dispersed therein, the silicon structures having been at least partially isolated from the aluminum-based metal of the alloy by selective etching of the aluminum-based metal of the alloy, and

the silicon structures comprise silicon-comprising structural elements, wherein 30 to 100% of the structural elements are high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension.

2. An electroactive material according to claim 1, wherein the high-aspect ratio structural elements have a minor dimension of at least 0.1 to 2 μ

m.

3. An electroactive material according to claim 1, wherein the structural elements have a major dimension of at least 5 μ

m.

4. An electroactive material according to claim 1, wherein 30 to 100% of the structural elements are high-aspect ratio structural elements having a minor dimension of 0.1 to 2 μ

m and a length of at least 10 times the minor dimension.

5. An electroactive material according to claim 1, wherein the structural elements are selected from the group consisting of flakes, fibres, stars and spikes.

6. An electroactive material according to claim 1, wherein the silicon structures comprise an agglomeration of the structural elements.

7. An electroactive material according to claim 6, wherein the structural elements are integrally connected and are in the form of a honeycomb structure.

8. An electroactive material according to claim 1, which further comprises residual metal from the aluminum-based metal-silicon alloy.

9. An electroactive material according to claim 8, wherein the residual metal is aluminum or an aluminum silicide intermetallic.

10. An electroactive material according to claim 1, wherein the silicon structures further comprise a carbon coating.

11. An electroactive material according to claim 1, wherein at least 80% of the structural elements are high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension.

12. An electroactive material according to claim 1, wherein the silicon structures have a porosity of 60 to 70%.

13. An electroactive material according to claim 1, which further comprises one or more components selected from a binder and a conductive carbon.

14. An electrode for a lithium-ion battery comprising the electroactive material according to claim 1.

15. An electrochemical cell comprising an electrode according to claim 14 and a cathode.

16. An electroactive material according to claim 1, wherein the solidified aluminum-based metal-silicon alloy is made by a method which comprises:

providing a molten aluminum-based metal silicon alloy having less than 30 wt % silicon, and

solidifying the molten aluminum-based metal silicon alloy.

24. An electroactive material according to claim 1, wherein the silicon structures have been at least partially isolated from a solidified aluminum-based metal-silicon alloy comprising 12-25% silicon.

25. An electroactive material according to claim 1, wherein the aluminum-based metal-silicon alloy is an Al—

Si alloy, an Al—

Mg—

Si alloy, or an Al—

Cu—

Si alloy.

26. An electroactive material according to claim 1, wherein the silicon structures are polycrystalline.

27. An electroactive material according to claim 1, wherein the structural elements are integral elements of a connected porous structure.

28. An electroactive material according to claim 1, wherein the silicon structures are isolated from the solidified aluminum-based metal-silicon alloy.

17. An electroactive material, made by a method which comprises:

providing a metal-silicon alloy comprising less than 30 wt % silicon, comprising an aluminum-based metal matrix, including an aluminum-based metal and silicon structures dispersed therein, the silicon structures comprising elongate structural elements having a minor dimension of less than 2 μ

m and an aspect ratio of at least 5; and

selectively etching the aluminum-based metal of the aluminum-based metal matrix to at least partially isolate the silicon structures, to provide silicon structures comprising an agglomeration of the elongate structural elements.

23. An electroactive material according to claim 17, wherein 30 to 100% of the structural elements are high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension.

29. An electroactive material according to claim 17, wherein the selective etching of the aluminum-based metal of the aluminum-based metal matrix isolates the silicon structures.

18. An electroactive material, comprising silicon-comprising structural elements, the silicon-comprising structural elements comprising high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension, the silicon-comprising structural elements being integrally connected to form a porous structure, and which further comprises residual metal, the residual metal comprising aluminum, an aluminum silicide intermetallic, or a combination thereof.

19. An electroactive material according to claim 18, wherein 30 to 100% of the structural elements are silicon-comprising structural elements comprising high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension.

20. An electroactive material according to claim 18, wherein at least 80% of the structural elements are high-aspect ratio structural elements having a minor dimension of less than 2 μ

m and a length of greater than 5 times the minor dimension.

21. An electroactive material according to claim 18, which has a porosity of 60 to 70%.

22. An electroactive material according to claim 18, wherein the structural elements comprise an agglomeration of integrally connected structural elements.