Synergistic Effect of LiBH4 and LiAlH4 Additives on Improved Hydrogen Storage Properties of Unexpected High Capacity Magnesium Hydride

A significant improvement in reversible de/rehydrogenation properties of MgH2 doped with 2.5 wt % LiAlH4 and 2.5 wt % LiBH4 additives is achieved by reactive ball milling. Careful comparison studies show that a small amount (total mass ratio of ≤5 wt %) of LiBH4 and/or LiAlH4 can improve the hydrogen desorption performance of MgH2 in terms of reducing hydrogen desorption temperature, enhancing hydrogen desorption kinetics, and increasing hydrogen capacity. In particular, the MgH2 co-doped with LiAlH4–LiBH4 exhibits the best dehydrogenation properties, which starts to release hydrogen at about 280 °C and releases a high hydrogen capacity of 7.62 wt % with superior reaction kinetics. The activation energy of hydrogen desorption is decreased from 187.8 kJ/mol (ball-milled MgH2) to 155.8 kJ/mol. It can also uptake 7.7 wt % H2 within 15 min at 300 °C with a stable hydrogen absorption kinetics in the first 10 cycles. This synergistic effect of LiBH4 and LiAlH4 additives on improved hydrogen absorption/desorptio...