Thelithium-ion secondary battery is also an environment-friendly battery that is free from heavy metals such as cadmium (Cd) or mercury (Hg) causing environmental contamination and rechargeable at least 500 times in a normal state so as to have a long uselife.Also, the lithium-ion secondary battery has an average discharge voltage of 3.6 to 3.7 V, which is advantageous to provide a very high power