Hydrogen storage properties of Li–Ca–N–H system with different molar ratios of LiNH2/CaH2

In this work, dehydrogenation and rehydrogenation of three LiNH2/CaH2 samples with LiNH2/CaH2 molar ratio of 2/1, 3/1 and 4/1 were systematically investigated. Remarkable differences were observed in the temperature dependence of hydrogen desorption and subsequent absorption. LiNH2/CaH2 in a molar ratio of 2/1 transforms to ternary imide Li2Ca(NH)2 after desorbing about 4.5 wt.% H2 at 350 °C. And it has a reversible hydrogen storage capacity of 2.7 wt.% at 200 °C. As for the LiNH2/CaH2 mixture in a molar ratio of 4/1, it transforms to a new compound with a composition of Li4CaN4H6 after being dehydrogenated at 350 °C. The rehydrogenation of both LiCa(NH)2 and Li4CaN4H6 gives LiNH2, LiH and the solid solution of 2CaNH–Ca(NH2)2.