Electronic structure and decomposition pathways of monoammoniate of lithium borohydride : A first-principles investigation

The monoammoniate of lithium borohydride (Li(NH3)BH4) is a potential candidate for hydrogen storage owing to its high hydrogen capacity (18 wt%). In this work, electronic structure, bonding characters, and decomposition pathways of Li(NH3)BH4 are investigated from first-principles calculations. We find that NH3 molecules are covalently attached to Li atoms through N atoms and the ionization of Li atoms plays an essential role in stabilizing the compound. A general correlation between the stability of X(NH3)BH4 (X=H,Li,Na,K) and the electronegativities of X atoms is established. The thermal stability of X(NH3)BH4 could be modulated by manipulating the cation electronegativities. Free energy computations indicate that Li(NH3)BH4→LiBH4+NH3 is the most likely thermal decomposition route.