Pressure and temperature dependence of the decomposition pathway of LiBH4

Abstract

The decomposition pathway is crucial for the applicability of LiBH₄ as a hydrogen storage material. We discuss and compare the different decomposition pathways of LiBH₄ according to the thermodynamic parameters and show the experimental ways to realize them. Two pathways, i.e. the direct decomposition into boron and the decomposition via Li₂B₁₂H₁₂, were realized under appropriate conditions, respectively. By applying a H₂ pressure of 50 bar at 873 K or 10 bar at 700 K, LiBH₄ is forced to decompose into Li₂B₁₂H₁₂. In a lower pressure range of 0.1 to 10 bar at 873 K and 800 K, the concurrence of both decomposition pathways is observed. Raman spectroscopy and ¹¹B MAS NMR measurements confirm the formation of an intermediate Li₂B₁₂H₁₂ phase (mostly Li₂B₁₂H₁₂ adducts, such as dimers or trimers) and amorphous boron.