| LiBH4 and its alloys have been considered to be one of the most promising materials for hydrogen storage because of their high storage capacity, low cost and light weight. However, The high sorption, desorption temperature and slow sorption kinetics limit their pratical applications. In order to develop LiBH4 into a practical hydrogen-storing material, we established the correspondence between micro physics like formation heat, substitutional solution heat as well as dissociation energy of hydrogen and macro performances like the structural stability of the alloy phase and dehydrogenation of alloys based on some experiments on the replaceable parts, acquired micro physical properties and electronic structure information of LiBH4 through first-principles calculations, then researched alloying effect of Mg, Al and Ti on dehydrogenation by replacing the Li atom in LiBH4 with these atoms, and explored the catalytic mechanism of dehydrogenation of LiBH4 systems based on the analysis on electronic mechanism.The equilibrium lattice constant, formation heat, electronic density of states, electron density and H atom dissociation energy of LiBH4 phase are calculated. The fairly good agreement between theoretical and experimental results show that the present calculations are highly reliable. When formation heat was a minus value, the negative alloy formations generate larger heats and mean it was difficult for dehydrogenation of LiBH4. In a LiBH4 alloy system, the Li-BH bond existed in the form of ionic bonds while the B-H bond was covalent, the violent formation may lead to difficulty in dehydrogenation of LiBH4.The equilibrium lattice constant, formation heat, electronic density of states, electron density and H atom dissociation energy of LiBH4 phase are also calculated, When substituting the Li atom with Mg, Al, Ti, the results showed that in minor substitution by alloying elements (like Mg, Al, Ti) energy consumption was maximum while Ti minimum, and the difficulty sequence is in oder of Ti, Mg, Al, Ti heat generated by the negative alloy was comparatively less than that after the alloying of LiBH4, which showed stability of the system was decreasing and alloying enhanced dehydrogenation capacity of the system.According to the LiBH4 alloying system, The decreasing of the formation heat of the LiBH4 systems is in order of Mg, Al, Ti, which showed the order of the improvement of dehydrogenating properties of LiBH4 system was Mg, Al, Ti, and Ti was best among them. When Ti was alloying, the amount of the electronic transfer decreased, the ionic bonds of Ti-LiBH4 became weaker, the covalent bond of Ti-LiBH4 became weaker while energy gap became narrow. In a LiBH4 alloy system, Ti alloy is best,according to the electron density analysis, the bonds of Ti-LiBH4 was weakest, and thought that the electrovalent bond and covalent bond became weaker, not the weakest, which may be the effect of the metal bond, or the effect of the composite bond.Formation heat of the second phase hydride, such as TiB2, A1B2, MgB2 are calculated.we found that the second phase hydride can be exist with better structural stability. The influences of second phase hydride TiB2, A1B2, MgB2 on the dehydrogenation properties of LiBH4 system are investigated by devising a supercell model of second phase hydride, and found that the second phase MgB2 improved the dehydrogenating properties of LiBH4 system. Compared with the existing experimental results, the exist of the second phase hydride and its catalysis in the dehydrogenation further confirmed the reliability of theoretical calculations as well as the accuracy of forecasting.
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