Lithium (LI) is the lightest metal in nature. Silver white, specific gravity 0.534, melting point 180 ℃, boiling point 1347 ℃, lithium is an active metal, very soft, and can spontaneously ignite in oxygen and air. Lithium is also an important energy metal. Its application in high-energy lithium batteries and controlled thermonuclear reactions makes lithium an important raw material to solve human long-term energy supply.