A METHOD OF FABRICATING STRUCTURED PARTICLES COMPOSED OF SILICON OR A SILICON-BASED MATERIAL AND THEIR USE IN LITHIUM RECHARGEABLE BATTERIES

• US 20110269019A1
• Filed: 10/02/2009
• Published: 11/03/2011
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Nexeon Limited
• Original Assignee: Nexeon Limited
• Inventors: Liu, Feng-Ming, Green, Mino
• Granted Patent: US 9,184,438 B2
• Time in Patent Office: Days
• US Class Current: 429/218.1
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 2004/028 Positive electrodes
• CPC Class Codes: H01M 4/049 Manufacturing of an active layer by chemical means
• 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 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/362 Composites
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A process for etching silicon to form silicon pillars on the etched surfaces, includes treating silicon with an etching solution that includes 5 to 10M HF 0.01 to 0.1M Ag⁺ ions and 0.02 to 0.2M NO₃⁻ ions. Further, NO₃⁻ ions in the form of alkali metal, nitric acid or ammonium nitrate salt is added to maintain the concentration of nitrate ions within the above range. The etched silicon is separated from the solution. The process provides pillars, especially for use as the active anode material in lithium ion batteries. The process is advantageous because it uses an etching bath containing only a small number of ingredients whose concentration needs to be controlled and it can be less expensive to operate than previous processes.

Claims

1. A process of etching silicon to form silicon pillars on the etched surfaces, the process comprising:

treating silicon with an etching solution comprising;

5 to 10M HF

0.01 to 0.1M Ag⁺ ions

0.02 to 0.2M NO₃⁻

ions and

adding further NO₃⁻

ions in the form of an alkali metal, nitric acid, or ammonium nitrate salt, to maintain the concentration of nitrate ions within the above range; and

separating the etched silicon from the solution.

2. The process of claim 1, wherein the further NO₃⁻

ions are added in the form of an alkali metal, nitrate salt, or ammonium nitrate.

3. The process of claim 1, wherein the solution contains less than 0.05% by weight of iron ions (ferric or ferrous).

4. The process of claim 1, wherein the solution is contains less than 0.5% by volume of an alcohol.

5. The process of claim 1, wherein the solution consists essentially of:

5 to 10M HF

0.01 to 0.1M Ag⁺ ions

0.02 to 0.2M NO₃⁻

ions

water, hydrogen and hydroxyl ions

and optionally

SiF₆²⁻

ions

alkali metal or ammonium ions, and

incidental additions and impurities.

6. The process of claim 1, which is conducted in a single bath.

14. The process of claim 1, wherein the solution used initially has a concentration of HF of 6.5 to 9M.

17. The process of claim 1, which includes the step of adjusting the composition by adding a base, preferably NaOH or NH₄OH, or nitric acid.

20. An electrode containing etched particles or fibres made by the process as defined in claim 1 as one of its active materials.

23. An electrochemical cell containing an anode as claimed in claim 20 and a cathode comprising a lithium-containing compound capable of releasing and reabsorbing lithium ions as its active material.

31. The process of claim 1, wherein the silicon that is treated with said etching solution is in the form of granules or bulk material.

32. The process of claim 1, wherein the silicon has a purity of 90.00% or over by mass.

33. The process of claim 1, wherein the silicon is in granular form.

34. The process of claim 33, wherein the granules have a particle size in the range 5 to 500 μ

m to produce silicon particles having pillars formed on their surfaces, the pillars having a height in the range of 1 to 100 μ

m.

35. The process of claim 1 wherein the pillars have a diameter at their bases in the range of 0.08 to 0.70 μ

m.

36. The process of claim 1, which includes the step of detaching the pillars from the underlying silicon to form silicon fibres.

37. The electrode as claimed in claim 20 wherein the etched silicon particles or fibres are incorporated into a complete film on a current collector.

7-13. -13. (canceled)

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