Anode active material, method of preparing the same, and lithium secondary battery including the anode active material

1. An anode active material comprising a silicon aluminum alloy comprising aluminum at about 60 wt % to about 80 wt %,

wherein the silicon aluminum alloy is heat-treated without coagulating the silicon, and acid-etched to be a porous silicon having pores with a uniform average pore diameter of about 60 nm to about 80 nm.

2. The anode active material of claim 1 , wherein a porosity of the porous silicon is in a range of about 45% to about 60%.

3. The anode active material of claim 1 , wherein D50 of silicon of the pores of the porous silicon is in a range of about 45 nm to about 65 nm, D90 is in a range of about 45 nm to about 55 nm, and D10 is in a range of about 60 nm to about 70 nm.

4. The anode active material of claim 1 , wherein an average particle diameter of the porous silicon is in a range of about 10 nm to about 100 μm.

5. The anode active material of claim 1 , wherein the average pore diameter of the pores of the porous silicon is in a range of about 60 nm to about 70 nm.

6. The anode active material of claim 1 , wherein the pores are heat-treated and acid etched pores.

7. A lithium secondary battery comprising:

a cathode;

an anode containing an anode active material comprising a silicon aluminum alloy comprising aluminum at about 60 wt % to about 80 wt %, wherein the silicon aluminum alloy is heat-treated without coagulating the silicon and acid-etched to be a porous silicon having pores with a uniform average pore diameter, wherein the average pore diameter is in a range of about 60 nm to about 80 nm; and

an electrolyte disposed between the cathode and the anode.

8. The lithium secondary battery of claim 7 , wherein a porosity of the porous silicon is in a range of about 45% to about 60%.

9. The lithium secondary battery of claim 7 , wherein D50 of silicon of the pores of the porous silicon is in a range of about 45 nm to about 65 nm, D90 is in a range of about 45 nm to about 55 nm, and D10 is in a range of about 60 nm to about 70 nm.

10. The lithium secondary battery of claim 7 , wherein an average particle diameter of the porous silicon is in a range of about 10 nm to about 100 μm.

11. The lithium secondary battery of claim 7 , wherein the average pore diameter of the pores of the porous silicon is in a range of about 60 nm to about 70 nm.

12. A method of preparing the anode active material of claim 1 , the method comprising:

heat-treating the silicon aluminum alloy in an inert gas atmosphere and

selectively removing the aluminum by performing etching on a resultant of the heat treated silicon aluminum alloy with an acidic solution.

13. The method of claim 12 , wherein a content of aluminum in the silicon aluminum alloy is about 60 wt %.

14. The method of claim 12 , wherein the acidic solution is a hydrochloric acid aqueous solution at a concentration of about 5 wt % to about 35 wt %.

15. The method of claim 12 , further comprising washing the resultant with distilled water or alcohol.