Effect of LiBH_4 on hydrogen storage property of MgH_2

摘要

The effect of lithium borohydride (LiBH_4) on the hydriding/dehydriding kinetics and thermodynamics of magnesium hydride (MgH_2) was investigated. It was found that LiBH_4 played both positive and negative effects on the hydrogen sorption of MgH_2. With 10 mol.% LiBH_4 content, MgH_2-10 mol.% LiBH_4 had superior hydrogen absorption/desorption properties, which could absorb 6.8 wt.% H within 1300 s at 200 ℃ under 3 MPa H_2 and completed desorption within 740 s at 350 ℃. However, with the increasing amount of LiBH_4, the hy-drogenation/dehydrogenation kinetics deteriorated, and the starting desorption temperature increased and the hysteresis of the pressure-composition isotherm (PCI) became larger. Our results showed that the positive effect of LiBH_4 was mainly attributed to the more uniform powder mixture with smaller particle size, while the negative effect of LiBH_4 might be caused by the H-H exchange between LiBH_4 and MgH_2.