Hydrogen Desorption/Absorption Properties of Li-Ca-N-H System

Hydrogen storage properties of two ball-milled composites of Ca(NH2)2+2LiH and CaH2+2LiNH2 were investigated as a series of searching studies of high performance hydrogen storage materials. About 4.5 mass% hydrogen is desorbed from about 100 °C and the thermal desorption profiles show a peak around 200 and 220 °C for the composites of CaH2+2LiNH2 and Ca(NH2)2+2LiH, respectively, under a helium flow at 5 °C/min heating rate without any NH3 emission within our experimental accuracy. The powder X-ray diffraction and infrared absorption spectroscopy indicated that the dehydrogenated states of both composites form “an unknown imide phase” after heating up to 400 °C, while the dehydrogenated states after heating up to 200 °C in vacuum are the mixed phases of Li2NH and CaNH.