Hydrogen storage in a Li–Al–N ternary system

Hydrogen-storage properties and mechanisms of a novel Li–Al–N ternary system were systematically investigated by a series of performance evaluation and structural examinations. It is found that ca. 5.2 wt% of hydrogen is reversibly stored in a Li3N–AlN (1:1) system, and the hydrogenated product is composed of LiNH2, LiH, and AlN. A stepwise reaction is ascertained for the dehydrogenation of the hydrogenated Li3N–AlN sample, and AlN is found reacting only in the second step to form the final product Li3AlN2. The calculation of the reaction enthalpy change indicates that the two-step dehydrogenation reaction is more thermodynamically favorable than any one-step reaction. Further investigations exhibit that the presence of AlN in the LiNH2–2LiH system enhances the kinetics of its first-step dehydrogenation with a 10% reduction in the activation energy due likely to the higher diffusivity of lithium and hydrogen within AlN.