Abstract
The aim of this work is to study the effects of bonding in Li-based hydrides in order to improve hydrogen storage properties. The tendency of (Li, H) atoms to form covalent bonding with (C, Si, Ge) atoms results in an improved reversibility of hydrogen in Li7XH8 (where X = C, Si, and Ge) compared to the LiH hydride. This bonding is considered to be stronger than the ionic bonding along Li-H. The structural and electronic properties of the hydrides Li7XH8 (X = C, Si, Ge) were investigated using the density functional theory and the full-potential linearised augmented plane wave. The covalent bonding tendency along Li-(C, Si, Ge) and along H-(C, Si, Ge) lowers formation energy values and leads to a decrease in desorption temperatures and stability of the hydrides Li7XH8 compared to the LiH hydride. The most hydrogen reversible compound having high gravimetric hydrogen storage was found to be Li7CH8 among all studied hydrides. In addition, the Li7CH8 hydride has smaller lattice parameters and smaller desorption temperature than the others. The calculated electronic densities of states and electron spatial distributions support this picture.
Published Version
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