Microstructural evolution and improved hydrogen storage properties for the Li3N–MgH2 system by addition of LiNH2 during the hydrogenation/dehydrogenation

Abstract

The Li–Mg–N–H system consists of lightweight materials with high hydrogen capacity and thus it is of interest for hydrogen storage application. In this work, different amount of LiNH2 in the Li3N–MgH2 (1:1) system was added to enhance the hydrogen storage properties. The mixtures of LiMgN, LiH and LiNH2 were obtained after ball milling of Li3N–MgH2-xLiNH2 (x = 0, 0.13, 1 and 2 mol). The addition of LiNH2 results in the microstructural change of dispersion of the particles with the refined grains, shortening of the diffusion distance of hydrogen. The hydrogen absorption/desorption capacities of all samples were greatly improved by the addition of LiNH2. The hydrogen storage capacity was improved from 3.2 wt% to approximately 5.1 wt% at 250 °C by the addition of LiNH2 from 0 to 2 mol. The microstructural evolution and hydrogen storage mechanisms during the hydrogenation/dehydrogenation process for the Li3N–MgH2–2LiNH2 sample are discussed.