Compaction pressure influence on material properties and sorption behaviour of LiBH4–MgH2 composite

Abstract

Among different Reactive Hydride Composites (RHCs), the combination of LiBH 4 and MgH 2 is a promising one for hydrogen storage, providing a high reversible storage capacity. During desorption of both LiBH 4 and MgH 2 , the formation of MgB 2 lowers the overall reaction enthalpy. In this work, the material has been compacted to pellets for further improvement of the volumetric hydrogen capacity. The influence of compaction pressure on the apparent density, thermal conductivity and sorption behaviour for the Li-based RHC during cycling has been investigated for the first time. Although LiBH 4 melts during cycling, decrepitation or disaggregation of the pellets is not observed for any of the investigated compaction pressures. However, a strong influence of the compaction pressure on the apparent hydrogen storage capacity is detected. The influence on the reaction kinetics is rather low. To provide explanations for the observed correlations, SEM analysis before and after each sorption step was performed for different compaction pressures. Thus, the low hydrogen sorption in the first cycles and the continuously improving sorption for low pressure compacted pellets with cycling may be explained by some surface observations, along with the form stability of the pellets.

Effect of the Process Parameters on the Energy Transfer during the Synthesis of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage

“…The determination of the theoretical density for the solid composite ρ solid , was displayed in a previous work [50] without the addition of TiCl 3 . The calculated particle size is displayed in Figure A2 versus the absorption ( Figure A2a) and desorption kinetic ( Figure A2b).…”

Complex and liquid hydrides for energy storage

“…One very well-known and intensively studied system is the 2LiBH 4 -MgH 2 system [102,205]. It shows a reversible hydrogen storage capacity in the range of 8-11 wt% and rather stable cycling properties [206]. Due to the lowered amount of reaction enthalpy, which accounts to 40-50 kJ/mol H 2 [102,207] during hydrogenation, much less heat is produced if compared with both LiBH 4 and MgH 2 , and dehydrogenation is possible at temperature and pressure conditions that are not suitable for dehydrogenation of the single LiBH 4 [208,209].…”

Tetrahydroborates: Development and Potential as Hydrogen Storage Medium

“…2LiBH 4 + MgH 2 2LiH + MgB 2 + 4H 2 (52) In the last decade this system has been thoroughly investigated with respect to reaction pathway, temperature and hydrogen pressure boundaries, microstructure, effect of additives on the reaction kinetics, and nanoconfinement [159][160][161][162][163][164][165][166][167][168][169][170][171][172][173].…”