Negative active material for lithium secondary battery and method for preparating same

An anode active material for a lithium secondary battery comprising a complex composed of Si phase particles and an oxide surrounding the Si phase particles.

A method for preparing an anode active material for a lithium secondary battery comprising:

• producing a complex composed of ultra-fine Si particles and an oxide surrounding the ultra-fine Si particles by mixing a silicon oxide and a material having an absolute value of oxide formation enthalpy (ΔHfor) greater than that of the silicon oxide and also a negative oxide formation enthalpy by a mechanochemical process or subjecting them to a thermochemical reaction to reduce the silicon oxide;
• and
• mixing the complex and carbon material.

A method for preparing an anode active material for a lithium secondary battery comprising:

• a process of producing a complex composed of ultra-fine Si particles and an oxide surrounding the ultra-fine Si particles by mixing a silicon oxide and a material having an absolute value of oxide formation enthalpy (ΔHfor) greater than that of the silicon oxide and also a negative oxide formation enthalpy by a mechanochemical process or subjecting them to a thermochemical reaction to reduce the silicon oxide.