Abstract: A method for transforming silicon slag into an anode material in lithium-ion batteries, comprising applying mechanical grinding, such as high-energy ball milling, to reduce particle size of silicon slag to micron and submicron sizes and/or to increase the amorphicity of the silicon slag powder. The silicon slag being used as raw material in fabricating the anodes has a composition of Si—SiC—C—SiO2, preferably having Si phase in both crystalline and amorphous states, and more preferably having Si phase only in amorphous state after a high-energy ball-milling thereof. The silicon slag has preferably a median particle diameter ?20 ?m after a high-energy ball-milling thereof and ?2 ?m after a slurry homogenization thereof. The silicon slag preferably contains 64% wt. Si+31% wt SiC+4% wt. C+1% wt. SiO2.