In situ formation of lithium fast-ion conductors and improved hydrogen desorption properties of the LiNH2-MgH2 system with the addition of lithium halides

Lithium halides were introduced into the LiNH2-MgH2 system by ball milling the corresponding chemicals under 50 bar of H-2 to decrease the dehydrogenation temperature and enhance the dehydrogenation kinetics. The results show that the LiNH2-MgH2-0.05LiBr sample exhibited optimal hydrogen storage performance. The onset dehydrogenation temperature of the LiNH2-MgH2-0.05LiBr sample was only 120 degrees C, which represents a 55 degrees C reduction with respect to that of the pristine LiNH2-MgH2 sample. The dehydrogenation rate of the LiNH2-MgH2 sample at 210 degrees C was increased threefold upon addition of LiBr, which is attributed to the reduction in the dehydrogenation activation energy. Moreover, the addition of LiBr could significantly suppress ammonia emission during the dehydrogenation process of the LiNH2-MgH2 sample. Structural examinations reveal that the added LiBr could react with LiNH2 to form Li-7(NH2)(6)Br during the dehydrogenation process. The in situ-formed Li-7(NH2)(6)Br not only weakens the N-H bond but also promotes the migration of Li+, consequently improving the dehydrogenation kinetics of the LiNH2-MgH2 sample.