Enhanced hydrogen storage properties of MgH2 with the co-addition of LiBH4 and YNi5 alloy

Abstract

MgH2, as one of the typical solid-state hydrogen storage materials, has attracted extensive attention. However, the slow kinetics and poor cycle stability limit its application. In this work, LiBH4 and YNi5 alloy were co-added as additives to MgH2 via ball milling, thereby realizing an excellent dehydrogenation performance and good cycle stability at 300 °C. The MgH2-0.04LiBH4-0.01YNi5 composite can release 7 wt.% of hydrogen in around 10 min at 300 °C and still have a reversible hydrogen storage capacity of 6.42 wt.% after 110 cycles, with a capacity retention rate as high as 90.3 % based on the second dehydrogenation capacity. The FTIR results show that LiBH4 can reversibly absorb and desorb hydrogen throughout the hydrogen ab/desorption process, which contributes a portion of the reversible hydrogen storage capacity to the MgH2-0.04LiBH4-0.01YNi5 composite. Due to the small amount of LiBH4 and YNi5, the dehydrogenation activation energy of MgH2 did not decrease significantly, nor did the dehydrogenation enthalpy (∆H) change. However, the MgNi3B2 and in-situ formed YH3 during the hydrogen absorption/desorption cycles is not only beneficial to the improvement of the kinetics performance for MgH2 but also improves its cycle stability. This work provides a straightforward method for developing high reversible hydrogen capacity on Mg-based hydrogen storage materials with moderate kinetic performance.