Negative active material for rechargeable lithium battery, method preparing the same and rechargeable lithium battery including the same

A negative active material comprising:

• surface modified silicon oxide particles having a bulk formula represented by SiOx (0.6≤x≤0.95), said particles comprising a surface and a surface region having a depth wherein the depth of the surface region is from 2 nm to 40 nm from the surface, wherein a silicon-to-oxygen ratio (Si/O ratio) of the surface region ranges from about 1.8 to about 2.0, wherein oxygen has an increasing concentration profile within the depth from the surface, whereas silicon has a decreasing concentration profile within the depth from the surface, wherein the negative active material has an average particle diameter ranging from about 0.1 μm to about 100 μm, and wherein the negative active material has a specific surface area ranging from about 5 m2/g to about 500 m2/g.