It is very reactive (as it is in the first column of the periodic table - Alkali metal). Other group of very reactive elements are in the second-last column su

It is very reactive (as it is in the first column of the periodic table - Alkali metal). Other group of very reactive elements are in the second-last column such as Fluorine but they can't be as easily used in batteries for other reasons. Lithium is also very light - 0.534 g/cm³ compared to copper with 8.96 g/cm³.