Negative electrode active material, negative electrode including the same, secondary battery including the negative electrode, and preparation method of the negative electrode active material

A method for preparing a negative electrode active material, comprising:

• preparing a silicon-based compound comprising SiOx, wherein 0.5<x<1.3;
• and
• forming a crystalline carbon coating layer on the silicon-based compound through a chemical vapor deposition method using an organometallic compound as a source, wherein
• the organometallic compound is at least any one selected from the group consisting of aluminum acetylacetonate, aluminum ethoxide, aluminum phenoxide, aluminum acetate, aluminum tributoxide, and a combination thereof, and
• wherein aluminum is present in the crystalline carbon coating layer in an amount of 3 parts by weight to 10 parts by weight based upon 100 parts by weight of the crystalline carbon coating layer.