  We present a first-principles study of the formation and migration of native
defects in lithium hydride (LiH), a material of interest in hydrogen storage
and lithium-ion batteries. We find that the negatively charged lithium vacancy
and positively charged hydrogen vacancy are the dominant defects in LiH with a
formation energy of about 0.85 eV. With this low energy, LiH can be a good
provider of Li$^+$ and/or H$^-$ ions. Based on our results, we discuss the role
of LiH in its reactions with another reactant which are important in hydrogen
storage and lithium-ion batteries, and explain the ionic conductivity and
hydrogen surface loss as observed in experiments.
