Pressure and temperature dependence of the decomposition pathway of LiBH4

The decomposition pathway is crucial for the applicability of LiBH4 as a hydrogen storage material. We discuss and compare the different decomposition pathways of LiBH4 according to the thermodynamic parameters and show the experimental ways to realize them. Two pathways, i.e. the direct decomposition into boron and the decomposition via Li2B12H12, were realized under appropriate conditions, respectively. By applying a H-2 pressure of 50 bar at 873 K or 10 bar at 700 K, LiBH4 is forced to decompose into Li2B12H12. In a lower pressure range of 0.1 to 10 bar at 873 K and 800 K, the concurrence of both decomposition pathways is observed. Raman spectroscopy and B-11 MAS NMR measurements confirm the formation of an intermediate Li2B12H12 phase (mostly Li2B12H12 adducts, such as dimers or trimers) and amorphous boron.