Enhanced dehydrogenation performances and mechanism of LiBH4/Mg17Al12-hydride composite

Abstract Mg 17 Al 12 -hydride (abbreviated as MAH) was selected as a destabilization agent to improve de/rehydrogenation properties of LiBH 4 . 58LiBH 4 +Mg 17 Al 12 -hydride composite was prepared by ball-milling. It is found that the dehydrogenation of ball-milled LiBH 4 /MAH composite presents a two-step reaction for hydrogen release. The composite starts desorbing hydrogen at about 300 °C and yields 9.8% of hydrogen (mass fraction) below 500 °C. By adding MAH, the dehydrogenation kinetics of LiBH 4 is improved and the dehydrogenation temperature of LiBH 4 is also lowered by 20 °C. High rehydriding capacity of 8.3% was obtained for the dehydrogenated composite in the first cycle at 450 °C. The XRD analysis shows the formation of MgB 2 and AlB 2 in the dehydrogenation process, which reduces the thermodynamics stability of LiBH 4 system and is beneficial to the reversible hydrogen storage behaviors of LiBH 4 /MAH composite.