| 摘要 |
A negative electrode active material includes an intermetallic compound. The intermetallic compound has a long period order along each of at least two crystal axes. The intermetallic compound is represented by formula (1) given below: <?in-line-formulae description="In-line Formulae" end="lead"?>LnM1<SUB>y</SUB>M2<SUB>z</SUB> ( 1 ) <?in-line-formulae description="In-line Formulae" end="tail"?> where y and z fall within the ranges of 0.3<=y<=1 and 2<=z<=3, respectively, Ln denotes at least one element having an atomic radius in crystal in a range of 1.6x10<SUP>-10 </SUP>to 2.2x10<SUP>-10 </SUP>m, M1 denotes at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Nb, and M2 denotes at least one element selected from the group consisting of P, Si, Ge, Sn and Sb.
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