Negative electrode active material for lithium secondary battery and negative electrode for lithium secondary battery

摘要

The present invention relates to a negative electrode active material for a lithium secondary battery, which has a composition containing Si in an amount of from 30 to 65% by mass and has a two phase matrix structure including an Sn—Cu based alloy matrix having an Sn content of 50% by mass or more, Si crystallites dispersed in the Sn—Cu based alloy matrix and an Si—X based alloy crystallized so as to at least partially cover the Si crystallites, in which X is at least one element selected from Fe, Ni and Co and is added in the Si—X based alloy in an amount of 1% by mass or more.