Hydrogen is regarded as a promising energy carrier for the current and future energetic and environmental problems. One of the main constraints for the practical application of hydrogen as energy carrier is the lack of an efficient and safe hydrogen storage system. Hydrogen storage in solid state through hydride compounds formation (MHx, M: Metal, H: Hydrogen) provides a potential alternative to address these problems. In this work, fundamental aspects of the physical chemistry of novel lithium hydride systems: Li-BMg-N, Li-B-Mg-Cu and Li-B-Mg-Zn are investigated. These systems are prepared via mechanical milling using as starting materials mixtures composed of MgB2+LizXy (X: Metal or Non-Metal). In order to understand reaction mechanism of these lithium hydride composite systems, experimental techniques such as thermogravimetry combined with differential temperature analysis and coupled with mass spectroscopy (TG-DTS-MS), exsitu and in-situ XRD and titration measurements are utilized. The Li-B-Mg-N and Li-BMg- Cu systems show the presence of crystalline LiBH4 after the first hydrogenation at 50 bar and 400 ºC. Hydrogen release for both systems is noticed at temperatures of about 300 ºC and 100 ºC upon the first and second non-isothermal dehydrogenation, respectively. Li-B-Mg-N system exhibits about 5 wt. % of reversible hydrogen storage capacity. LiBH4 and an amorphous Li-B-N-H containing phase are the reversible hydride compounds.