New insights into the thermodynamic behavior of 2LiBH4-MgH2 composite for hydrogen storage

Abstract

The composite 2LiBH4: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 °C. Different reaction paths which have important implication for storage applications during hydrogen absorption and desorption at various temperatures were revealed. At temperatures over 413°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 H2, LiH, and MgB2 at lower pressures. On the other hand, at temperatures below 413°C only one plateau is present in the system. During desorption, the double plateau can be observed at temperatures as low as 375°C. This effect restricts the applicability of this composite as a hydrogen storage material.