The microstructure of nanometer-scale tin powder synthesized by the wire electric explosion (WEE) method is examined by transmission electron microscopy (TEM) at different Li insertion states, and then electrochemical properties of the tin power electrode are characterized by galvanostatic charge–discharge experiments. It is found that several Li/Sn inter-metalic compounds are formed during lithium insertion, namely Li1−x Sn, L13Sn5 and Li7Sn2. The passivation layer (or solid electrolyte interface, SEI) on the surface of particles cycled in an organic electrolyte electrochemical cell is characterized as Li2CO3 and ROCO2Li by FT-IR spectroscopy. A great part of the passivation layer is amorphous, but a small is poorly crystallized.