What are the extensive uses of Lithium compounds?

Outer layer of elements as lithium, sodium and potassium, contains a single electron. These elements combine very easily with other elements (transferring them the electron from their last layer) forming a large number of chemical compounds.
Lithium is found very little spread in nature. The accompanying small quantities in some rocks potassium and sodium, lithium and aluminum silicate, LiAl [SiO3] 2, fluoro-or hydroxy-aluminosilicates of lithium, potassium and aluminum Li3K2Al3 [Al (Si3O10) 2 (OH, F) 4] , and a variety of lepidolit much iron, etc..

Lithium decompose water and ignites in air  forming lithium oxide, Li2O.Heated in hydrogen atmosphere formes lithium hydride, LIH, which is the most stable of the alkali metal hydrides.
Lithium is the only alkali metal that combines directly with nitrogen in cool atmosphere, forming nitrides, Li3N, also directly combine with halogens to form halides in  hot atmosphere, LIX, sulfur, forming sulfur, Li2S, with carbon, forming carbides, Li2C2, with silicon, forming silicides, Li6Si2, etc..