The hydrogen storage properties and mechanisms of the Ca(BH4)(2)-added 2LiNH(2)-MgH2 system were systematically investigated. The results showed that the addition of Ca(BH4)(2) pronouncedly improved hydrogen storage properties of the 2LiNH(2)-MgH2 system. The onset temperature for dehydrogenation of the 2LiNH(2)-MgH2-0.3Ca(BH4)(2) sample is only 80 degrees C, a ca. 40 degrees C decline with respect to the pristine sample. Further hydrogenation examination indicated that the dehydrogenated 2LiNH(2)-MgH2-0.1Ca(BH4)(2) sample could absorb ca. 4.7 wt% of hydrogen at 160 degrees C and 100 atm while only 0.8 wt% of hydrogen was recharged into the dehydrogenated pristine sample under the same conditions. Structural analyses revealed that during ball milling, a metathesis reaction between Ca(BH4)(2) and LiNH2 firstly occurred to convert to Ca(NH2)(2) and LiBH4, and then, the newly developed LiBH4 reacted with LiNH2 to form Li-4(BH4)(NH2)(3). Upon heating, the in situ formed Ca(NH2)(2) and Li-4(BH4)(NH2)(3) work together to significantly decrease the operating temperatures for hydrogen storage in the Ca(BH4)(2)-added 2LiNH(2)-MgH2 system. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.