ELECTRICAL-DEVICE-USE NEGATIVE-ELECTRODE ACTIVE SUBSTANCE

A negative electrode active material for an electric device according to the present invention includes crystalline metal having a structure in which a size in a perpendicular direction to a crystal slip plane is 500 nm or less. More preferably, the size in the perpendicular direction to the crystal slip plane is controlled to become 100 nm or less. As described above, a thickness in an orientation of the slip plane is controlled to become sufficiently small, and accordingly, micronization of the crystalline metal is suppressed even if breakage occurs from the slip plane taken as a starting point. Hence, a deterioration of a cycle lifetime can be prevented by applying the negative electrode active material for an electric device, which is as described above, or a negative electrode using the same, to an electric device, for example, such as a lithium ion secondary battery.