Negative electrode active material for non-aqueous electrolyte rechargeable battery, method for preparing same, and non-aqueous rechargeable battery including same

A negative electrode active material for a non-aqueous electrolyte rechargeable battery, comprising a silicon oxide composite, the silicon oxide composite containing i) silicon, ii) a silicon oxide represented by general formula SiOx (0<x<2), and iii) an oxide including silicon and Mg,

• wherein the silicon oxide composite exhibits at least one diffraction peak in each of the ranges of 27° to 32° and 21° to 23.5°, in the X-ray diffraction analysis, and
• wherein there is no peak by SiO2 in the X-ray diffraction analysis;
• wherein the negative electrode active material is manufactured by the method comprising:
• (i) simultaneously injecting a silicon oxide powder and Mg into a reactor, the silicon oxide powder being obtained by mixing silicon and silicon dioxide (SiO2) powders to have a mole ratio of 1:0.5 to 1:1.5, the mole ratio of the silicon and Mg being 1:0.01 to 1:1;
• (ii) heating the silicon oxide powder and Mg at 1,000-1,800° C., followed by cooling at 500-900° C., to precipitate a silicon oxide composite;
• and
• (iii) pulverizing the precipitated silicon oxide composite to an average particle diameter of 0.1-20 μm.