Method for preparing silicon-based active material particles for secondary battery and silicon-based active material particles

1. A method of preparing silicon-based active material particles, the method comprising:

providing silicon powders;

preparing a pre-pulverization mixture by dispersing the silicon powders in an oxidant solvent;

forming silicon particles by refining the silicon powders of the pre-pulverization mixture by applying mechanical compression and shearing stress to the silicon powders;

forming silicon-based active material particles by forming a chemical oxidation layer on the refined silicon particles by using the oxidant solvent while applying the mechanical compression and shearing stress, to provide a resulting product comprising the silicon-based active material particles; and

yielding the silicon-based active material particles by drying the resulting product,

wherein the silicon-based active material particles have a silicon crystal domain size of less than 50 nm.

2. The method of claim 1 , wherein the oxidant solvent comprises water, de-ionized water, an alcoholic solvent or a mixture of two or more thereof.

3. The method of claim 2 , wherein the alcoholic solvent comprises any one of ethyl alcohol, methyl alcohol, glycerol, propylene glycol, isopropyl alcohol, isobutyl alcohol, polyvinyl alcohol, cyclohexanol, octyl alcohol, decanol, hexatecanol, ethylene glycol, 1,2-octane diol, 1,2-dodecane diol, and 1,2-hexadecane diol, or a mixture thereof.

4. The method of claim 2 , wherein the alcoholic solvent is ethyl alcohol.

5. The method of claim 1 , wherein the applying of the mechanical compression and shearing stress is performed in a mill-pulverizing operation using a mixture of abrasive particles and the oxidant solvent.

6. The method of claim 1 , wherein the applying of the mechanical compression and shearing stresses is achieved by a grinding technique for providing the pre-pulverization mixture between a spinning abrasive plate and a fixed plate and performing pressing and polishing simultaneously.

7. The method of claim 1 , wherein the circularity of the silicon-based active material particles is equal to or greater than 0.5 and less than or equal to 0.9, and the circularity is determined according to Equation 1 below:

Circularity

=

2

⁢

π

⁢

⁢

A

P

[

Equation

⁢

⁢

1

]

(A denotes an area of projection of a 2-dimensionally projected silicon particle and P denotes the circumferential length of the 2-dimensionally projected silicon particle).

8. The method of claim 1 , wherein the core of the silicon particle has a solid-type shape, a fiber-type shape, or a tube-type shape.

9. The method of claim 1 , wherein the area of the {110} surface of the core of the silicon particle is greater than the area of the {100} surface and the area of the {111} surface.

10. The method of claim 9 , wherein the {110} surface of the core of the silicon particle is a pulverized surface of a polished surface.

11. The method of claim 1 , wherein an average diameter of the silicon-based active material particles is in the range of 30 nm to 300 nm.

12. The method of claim 1 , wherein oxygen content of the silicon-based active material particles with respect to the total weight of the silicon-based active material particles is limited to from 9 wt % to 20 wt %.

13. The method of claim 1 , wherein a conductive layer is further formed on the chemical oxidation layer.