The decomposition mechanisms of [Li(NH3)][BH4], [Al(NH3)(6)][BH4](3) and [Al(NH3)(6)][Li-2(BH4)(5)] were investigated using Density functional theory (DFT) calculation. The calculated results show that [Li(NH3)][BH4] has low NH3 vacancy formation energy and diffusion barrier, therefore ammonia would easily release at relatively low temperature. Both [Al(NH3)(6)] [BH4](3) and [Al(NH3)(6)]P-2(BH4)(3)] show relatively high NH3 vacancy formation energies and diffusion barriers, which avoid ammonia release at low temperature. In addition, the calculated H-2 formation energy barriers, i.e., [Al(NH3)(6)][Li-2(BH4)(5)] < [Al(NH3)(6)] [BH4](3) < [Li(NH3)][BH4], are in agreement with the tendency of dehydrogenation temperatures determined experimentally. The incorporation of [BH4](-) into [Al(NH3)(6)][BH4](3) play an important role in decreasing the dehydrogenation temperature and improving the hydrogen purity of [Al(NH3)(6)][Li-2(BH4](5)]. (C) 2017 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.