NEGATIVE ELECTRODE ACTIVE MATERIAL, PREPARATION METHOD THEREOF, AND NEGATIVE ELECTRODE AND SECONDARY BATTERY INCLUDING SAME

The present invention relates to a negative electrode active material including silicon-based oxide particles and a metal distributed on a surface, inside, or on the surface of and the inside the silicon-based oxide particles, wherein compressive fracture strength measured at a pressure of 100 mN is 170 MPa to 380 MPa, and the silicon-based oxide particles contain Si crystal grains having a crystal grain size of 3 nm to 20 nm.