▎ 摘　　要

NOVELTY - Porous silicon composite comprises silicon particles and a magnesium compound, where a molar ratio of oxygen atoms and silicon atoms in the porous silicon composite is 0.01-0.35. USE - The porous silicon composite is used for porous silicon-carbon composite for negative electrode active material for lithium secondary battery (all claimed). ADVANTAGE - The porous silicon composite has improved dispersion stability and mechanical properties such as strength, and improves discharge capacity and initial efficiency. The method has mass production through a continuous process with minimized steps. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a porous silicon-carbon composite comprising the porous silicon composite, and carbon; (2) a method for producing the porous silicon composite, which involves (i) obtaining a silicon composite oxide powder using a silicon-based raw material and a magnesium-based raw material, (ii) etching the silicon composite oxide powder using an etching solution containing a fluorine (F) atom-containing compound, and (iii) filtering and drying the composite obtained by the etching to obtain the porous silicon composite; (3) a method for producing the porous silicon-carbon composite, which involves (i) obtaining a silicon composite oxide powder using a silicon-based raw material and a magnesium-based raw material, (ii) etching the silicon composite oxide powder using an etching solution containing a fluorine (F) atom-containing compound, (iii) filtering and drying the composite obtained by the etching to obtain a porous silicon composite, and (iv) obtaining a porous silicon-carbon composite by forming a carbon layer on the surface of the porous silicon composite by using a chemical thermal decomposition deposition method; and (4) a negative electrode active material comprising the porous silicon-carbon composite.