Dehydriding and rehydriding reactions of LiBH4

Structural differences in LiBH4 before and after the melting reaction at approximately 550 K were investigated to clarify the experimental method for the confirmation of reversible dehydriding and rehydriding reactions. Since the long-range order of LiBH4 begins to disappear after the melting reaction was achieved, investigation of the atomistic vibrations of the [BH4]-anion in LiBH4 was found to be effective for the confirmation of the reversibility. In the present study, LiBH4 was successively dehydrided (decomposed) into LiH and B under 1 MPa of hydrogen at 873 K, and then rehydrided (recombined) into LiBH4 under 35 MPa of hydrogen at the same temperature (873 K). The temperatures at the beginning and ending of the dehydriding reaction are lowered, by approximately 30 K, for LiBH4 substituted (or mixed) with Mg (atomic ratio of Li:Mg=9:1) as compared to those for LiBH4 alone. This is similar to the tendency exhibited by LiNH2.