Effects of additives on the microstructure and hydrogen storage properties of the Li3N-MgH2 mixture

The Li-Mg-N-H system is a very promising hydrogen storage material due to its high capacity, reversibility and moderate operating conditions. In this work, the mixture of LiMgN and LiH produced by ball milling with a mixture of Li3N-MgH2 at a 1:1 M ratio starts to absorb hydrogen at 130 °C under 10 MPa. Effects of the additives (5 mol% Ti, 5 mol% TiCl3 and 5 mol% LiNH2) on the microstructural evolution and hydrogen storage properties were studied. Among the additives, Ti and TiCl3 are both detrimental for hydrogen storage properties including hydrogen absorption/desorption capacity and hydrogenation kinetics, but, LiNH2 is the most effective additive for improving the hydrogen storage properties. With an addition of 5 mol% LiNH2, the hydrogen absorption capacity is improved from 3.2 wt% to 3.7 wt% and the onset absorption temperature is decreased from 130 °C to 90 °C. The improvement of hydrogen properties is due to well-distributed nano-particles of the hydrogenated/dehydrogenated products.