Is Lithium hydride, ionic or covalent bonding?

Lithium and hydrogen are bonded together through ionic bonding.

Lithium is a metal; during ionic bonding, lithium loses an electron to become the ion #"Li"^(+)#. Hydrogen acquires an electron from lithium to become the ion #"H":^(-)#.

When they react, they each share their single valence electron to make a bond between the two atoms. It is reasonably polar (#"EN"_"H" = 2.2#, #"EN"_"Li" = 0.98#), which is why it is an ionic compound.

Lithium hydride does not exhibit many of the properties that we often associate with so-called "ionic" compounds. In the molten state its conductivity does not increase, indicating Li+ and H- ions do not form in the molten state. Nor does it dissolve in water to make Li+ ions and H- ions. Instead, it reacts violently with water producing hydrogen gas and a solution of lithium hydroxide. The 2s orbitals of Li and the 1s orbitals of H overlap within the octahedral network giving rise to bonds with significant covalent character.