Method of making silicon anode material for rechargeable cells

Patent metadata

Field	Value
Publication number	US-9553304-B2
Application number	US-201514597875-A
Country	US
Kind code	B2
Filing date	Jan 15, 2015
Priority date	May 7, 2009
Publication date	Jan 24, 2017
Grant date	Jan 24, 2017

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.

First claim

The invention claimed is:

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 μm 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 μm.

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

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 μm 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 μm 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.

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 μm 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.

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 μm 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 μm 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 μm 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.

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

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.

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.

Assignees

• Rayner Philip John
• Nexeon Ltd

Inventors

• Rayner Philip John

Classifications

• C22C21/02 Primary

  with silicon as the next major constituent · CPC title

• Y10T428/298

  Physical dimension · CPC title

• Y02E60/122

  Cross-Sectional Technologies · mapped topic

• H01M4/134 Primary

  Electrodes based on metals, Si or alloys · CPC title

• H01M4/0492

  Chemical attack of the support material · CPC title