Anode active material including a multilayer metal nanotube, anode including the anode active material, lithium battery including the anode, and method of preparing the anode active material

A method of preparing an anode active material, the method comprising:

• growing a metal oxide nanorod which extends away from a surface of a conductive substrate;
• forming a first metal layer comprising a first metal on the metal oxide nanorod to form a coated metal oxide nanorod;
• thermally treating the coated metal oxide nanorod to selectively remove the metal oxide nanorod and form a first metal nanotube;
• and
• forming a second metal layer comprising a second metal on the first metal nanotube to form a multilayer metal nanotube to prepare the anode active material,
• wherein the anode active material comprises a multilayer metal nanotube comprising
• an inner layer, and
• an outer layer on the inner layer,
• wherein the inner layer comprises a first metal having an atomic number equal to 13 or higher, and the outer layer comprises a second metal different from the first metal, and
• wherein the second metal has a resistivity which is less than a resistivity of the first metal.