NONAQUEOUS ELECTROLYTE SECONDARY BATTERY AND NEGATIVE ELECTRODE THEREOF

摘要

A negative electrode for nonaqueous electrolyte secondary battery of high performance that exhibits high discharge capacity and high charge/discharge efficiency in the initial stage and during the cycle operation, excelling in cycle characteristics, which electrode exhibits suppressed swelling after cycle operation. The negative electrode comprises an active material thin film of phase having elemental Z lying in Si in a nonequilibrium manner, the active material thin film composed mainly of a compound of the general formula SiZxMy (wherein Z, M, x and y satisfy the following requirements). The element Z is at least one element selected from the group consisting of B, C and N. The element M is at least one element, other than Si and the element Z, selected from the elements of Group 2, Group 4, Group 8, Group 9, Group 10, Group 11, Group 13, Group 14, Group 15 and Group 16 of the periodic table. x is such a value that with respect to the Z-concentration (p/(a+p)) of compound SiaZp (wherein a and p are integers) with composition closest to Si and being present in equilibrium, the Z-concentration ratio Q(Z) calculated by the formula Q(Z)=[x/(1+x)]/[p/(a+p)] is in the range of 0.10 to 0.95. y is a number satisfying the relationship 0<=y<=0.50.