Negative electrode active material for nonaqueous electrolyte secondary batteries

Abstract

A negative electrode active material for nonaqueous secondary batteries is disclosed. The active material contains a silicon solid solution having one or more than one of a group 3 semimetal or metal element, a group 4 semimetal or metal element except silicon, and a group 5 nonmetal or semimetal element incorporated in silicon as a solute element. The solute element is present more on the crystal grain boundaries of the silicon solid solution than inside the grains.

1 . A composite comprising a silicon solid solution and a silicon alloy,
 the a silicon solid solution having one or more than one element selected from a group 3 semimetal element, a group 4 semimetal element except silicon, and a group 5 semimetal   element incorporated in silicon,   the one or more than one element being present more on the crystal grain boundaries of the silicon solid solution than inside the crystal grains,   the silicon alloy being an alloy of silicon with a transition metal, and   the composite having the silicon solid solution as a matrix and a phase of the silicon alloy precipitated in the matrix.