Effects of compaction pressure and graphite content on hydrogen storage properties of Mg(NH2)2–2LiH hydride

•Mg(NH2)2–2LiH–0.07KOH–graphite compacts were prepared.•The desorption kinetics becomes stable from the 2nd sorption cycles on.•Compaction pressure just affects the desorption kinetics of the 1st sorption cycle.•The ENG addition significantly accelerates the desorption kinetics.•The volumetric hydrogen storage density increases obviously after compaction.

Preparation of hydride–graphite compacts serves as an effective method to improve the volumetric hydrogen storage density and the effective thermal conductivity for light complex hydrides. This paper presents the effects of compaction pressure and expanded natural graphite (ENG) content on the hydrogen storage properties of the Mg(NH2)2–2LiH–0.07KOH compacts. The results show that the hydrogen desorption kinetics of the 1st sorption cycle decreases with the increase of the compaction pressure. However, the compacts exhibit the similar hydrogen desorption kinetics and capacities from the 2nd sorption cycles on regardless of the compaction pressure. The ENG addition significantly enhances the desorption kinetics because of the improvement of the heat transfer performance of the hydride. Furthermore, the volumetric hydrogen storage density of the hydride reaches 47 g/L after the compaction at 365 MPa, but it reduces by increasing the ENG content.