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

Mg17Al12-hydride (abbreviated as MAH) was selected as a destabilization agent to improve de/rehydrogenation properties of LiBH4. 58LiBH4+Mg17Al12-hydride composite was prepared by ball-milling. It is found that the dehydrogenation of ball-milled LiBH4/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 LiBH4 is improved and the dehydrogenation temperature of LiBH4 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 MgB2 and AlB2 in the dehydrogenation process, which reduces the thermodynamics stability of LiBH4 system and is beneficial to the reversible hydrogen storage behaviors of LiBH4/MAH composite.