Negative electrode active material, negative electrode including same, secondary battery including same and method for preparing negative electrode active material

A negative electrode active material, comprising:

• particles comprising a silicon-containing oxide represented by SiOx, wherein 0<x<2;
• and
• lithium distributed in the particles,
• wherein the lithium is present in a form of (a) crystalline Li2Si2O5, and optionally one or more selected from (b) crystalline Li2SiO3, (c) crystalline Li4SiO4 or (d) amorphous lithium silicate,
• a content of the crystalline Li2Si2O5 is higher than the sum of a content of the crystalline Li2SiO3 and a content of the crystalline Li4SiO4, and
• a total content of the crystalline phase present in the particles is higher than a total content of the amorphous phase.