Abstract
In view of the decomposition of LiBH4-MgH2 involving LiBH4-Mg or Li2B12H12-Mg, in the present study, a comparative study on the dehydrogenation performance of Mg-doped LiBH4 and Li2B12H12 (the intermediate compound of individual decomposition of LiBH4) has been made using first-principles calculations. Our studies aim at providing new insights into the promoting hydrogen storage properties of LiBH4-MgH2. The results show that the properties of LiBH4 and Li2B12H12 can be modified by Mg resulting in favorable H-desorption, due to that LiB/H bond is weakened and MgB bond is formed as Mg addition. Nevertheless, it is noted that, compared to LiBH4 systems, (1) Li2B12H12 systems with relatively higher hydrogen dissociation energies are disadvantage to hydrogen desorption, due to the stronger BH, LiB and LiH bonds and the suppression of the formation of MgB2 upon dehydrogenation; (2) Li2B12H12 systems with unique BB bonds are unfavorable for hydrogen storage reversibility, since BB bonds is considered to be the main obstacle for rehydrogenation of metal borohydrides. From these, we believed that upon decomposition of LiBH4-MgH2, suppressing the formation of intermediate compound Li2B12H12 should be of great importance for further improvement of hydrogen storage properties of LiBH4-MgH2.
Published Version
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