The long-term hydriding and dehydriding stability of the nanoscale LiNH2+LiH hydrogen storage system.

The long-term cyclic durability of nano-engineered solid-state hydrogen storage systems is investigated using LiNH2+LiH as a model system. Through 60 hydriding and dehydriding cycles over the course of more than 200 h, a small decrease in the kinetics of the dehydrogenation reaction leads to a 10% reduction in the amount of hydrogen liberated during a 2.5 h desorption. Although a 75% loss in the specific surface area is encountered within the first 10 cycles, the crystallite size remains relatively stable near 20 nm while enduring 72% of the average melting temperature of the phases. The lack of microstructural growth is attributed to low packing efficiency of the ball milled powder in combination with the mixture of multiple phases present and repeated nucleation of fine grains during hydriding and dehydriding reactions.