New Insights into the Thermodynamic Behavior of 2LiBH4-MgH2 Composite for Hydrogen Storage

The composite 2LiBH(4):MgH2 has been studied as a potential hydrogen storage material due to its high storage capacity. The present work is aimed at clarifying the thermodynamic behavior of the system, especially within the temperature region above 400 degrees C. Different reaction paths which have important implication for storage applications during hydrogen absorption and desorption at vadous temperatures were revealed. At temperatures over 413 degrees C, two different absorption pressure plateaus are observed. This indicates that two different reactions occur: Mg hydrogenation at higher pressures and the re-formation of LiBH4 from H-2, LiH, and MgB2 at lower pressures. On the other hand, at temperatures below 413 degrees C only one plateau is present in the system. During desorption, the double plateau can be observed at temperatures as low as 375 degrees C. This effect restricts the applicability of this composite as a hydrogen storage material.