Enhanced hydrogen storage properties of 1.1MgH2-2LiNH2-0.1LiBH4 system with LaNi5-based alloy hydrides addition

Abstract

Significant improvements in the hydrogen sorption properties of the Li-Mg-N-H system have been achieved by adding a small amount of LiBH₄. Herein, the hydrogen storage properties of the 1.1MgH₂-2LiNH₂-0.1LiBH₄ system are further enhanced by addition of LaNi₅-based (LaNi_3.8Al_0.75Mn_0.45, LaNi_4.5Mn_0.5, LaNi₄Co) alloy hydrides. The refinement of the Li-Mg-B-N-H particles and the metathesis reaction are facilitated by adding LaNi₅-based alloy hydrides during the ball milling process. The addition of LaNi₅-based alloy hydrides can enhance the hydrogen sorption kinetics, reduce the dehydrogenation temperature and promote a more thorough dehydrogenation of the Li-Mg-B-N-H system. The LaNi₅-based alloy hydrides are involved in hydrogen de/hydrogenation reaction. Among the three alloys, LaNi_4.5Mn_0.5 makes the most obvious improvement on the reaction kinetics, and the dehydrogenation peak temperature is reduced by 12 °C, while the activation energy is reduced by 11% with 10 wt% LaNi_4.5Mn_0.5 addition. The weakening of the N-H bond and the homogeneous distribution of the LaNi₅-based alloy hydrides in the Li-Mg-B-N-H composite have important roles in the reduction of the desorption barrier and the kinetics enhancement.