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Lithium tetrahydridoboranate (LiBH 4 ) may be a potentially interesting material for hydrogen storage, but in order to absorb and desorb hydrogen routinely and reversibly, the kinetics and thermodynamics need to be improved significantly. A priori, this material has one of the highest theoretical gravimetric hydrogen contents, 18.5 wt %, but unfortunately for practical applications, hydrogen release occurs at too high temperature in a non-reversible way. By means of in situ synchrotron radiation powder X-ray diffraction (SR-PXD), the interaction between LiBH 4 and different additivessSiO 2 , TiCl 3 , LiCl, and Ausis investigated. It is found that silicon dioxide reacts with molten LiBH 4 and forms Li 2 SiO 3 or Li 4 SiO 4 at relatively low amounts of SiO 2 , e.g., with 5.0 and 9.9 mol % SiO 2 in LiBH 4 , whereas, for higher amounts of SiO 2 (e.g., 25.5 mol %), only the Li 2 SiO 3 phase is observed. Furthermore, we demonstrate that a solid-state reaction occurs between LiBH 4 and TiCl 3 to form LiCl at room temperature. At elevated temperatures, more LiCl is formed simultaneously with a decrease in the diffracted intensity from TiCl 3 . Lithium chloride shows some solubility in solid LiBH 4 at T > 100°C. This is the first report of substituents that accommodate the structure of LiBH 4 by a solid/solid dissolution reaction. Gold is found to react with molten LiBH 4 forming a Li-Au alloy with CuAu 3 -type structure. These studies demonstrate that molten LiBH 4 has a high reactivity, and finding a catalyst for this H-rich system may be a challenge.

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