A comparative study of LiBH4-based composites with metal hydrides and fluorides for hydrogen storage

A comparative study was performed on four LiBH 4 -based hydrogen storage composites 2LiBH 4  + MgX 2 and 6LiBH 4  + CaX 2 (X = H and F). The composites with fluorides and those with corresponding hydrides exhibited similar hydrogen storage properties. The dehydrogenation of 2LiBH 4  + MgF 2 demonstrated a strong dependence on the hydrogen back pressure , similar to that of 2LiBH 4  + MgH 2 . The reversible hydrogen storage of 2LiBH 4  + MgF 2 was achieved under a back pressure of 5 bar at 450 °C. Dehydrogenation under lower H 2 pressures resulted in the production of Mg and thus a partial reversibility. In contrast, both 6LiBH 4  + CaH 2 and 6LiBH 4  + CaF 2 revealed reversible hydrogen storage properties regardless of the hydrogen back pressure. The structural difference between MgB 2 and CaB 6 may account for the observed differences in hydrogen storage properties of the Mg- and Ca-containing LiBH 4 reactive composites.