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

A comparative study was performed on four LiBH4-based hydrogen storage composites 2LiBH4 + MgX2 and 6LiBH4 + CaX2 (X = H and F). The composites with fluorides and those with corresponding hydrides exhibited similar hydrogen storage properties. The dehydrogenation of 2LiBH4 + MgF2 demonstrated a strong dependence on the hydrogen back pressure, similar to that of 2LiBH4 + MgH2. The reversible hydrogen storage of 2LiBH4 + MgF2 was achieved under a back pressure of 5 bar at 450 °C. Dehydrogenation under lower H2 pressures resulted in the production of Mg and thus a partial reversibility. In contrast, both 6LiBH4 + CaH2 and 6LiBH4 + CaF2 revealed reversible hydrogen storage properties regardless of the hydrogen back pressure. The structural difference between MgB2 and CaB6 may account for the observed differences in hydrogen storage properties of the Mg- and Ca-containing LiBH4 reactive composites.