First-principles study on influence of alloying element substitution on dehydrogenation ability of Li4BN3H10 hydrogen storage materials

Abstract

A first-principles plane-wave pseudopotential method based on the density functional theory is used to investigate the dehydrogenation properties and the influence mechanism of Li4BN3H10 hydrogen storage materials. The binding energy, the density of states and the Mulliken overlap population are calculated. The results show that the binding energy of crystal has no direct correlation with the dehydrogenation ability of (LiM)4BN3H10(M=Ni,Ti,Al,Mg). The width of band gap and the energy level of impurity are key factors to affect the dehydrogenation properties of (LiM)4BN3H10 hydrogen storage materials: the wider the energy gap is, the more strongly the electron is bound to the bond, the more difficultly the bond breaks, and the higher wile the dehydrogenation temperature be. Alloying introduces the impurity energy level in band gap, which leads the Fermi level to enter into the conduction band and the bond to be weakened, thereby resulting in the improvement of the dehydrogenation properties of Li4BN3H10. It is found from the charge population analysis that the bond strengths of N—H and B—H are weakened by alloying, which improves the dehydrogenation properties of Li4BN3H10.