Local structure and dynamics in lithium borohydride

Lithium borohydride, LiBH4 is one of the promising materials for hydrogen storage due to its high gravimetric and volumetric hydrogen densities of 18.5 wt.% and 121 kg H2/m3, respectively, way above the 5.5 wt.%, regarded as the target for onboard hydrogen storage by the US Department of Energy (DOE). Solid LiBH4 has been attracting much interest as a material for renewable energy applications, first as a potential high-capacity hydrogen store and, more recently, as a solid-state lithium-ion conductor due to its superionic conductivity at high temperature. Despite the flurry of research activity, there still remains some degree of uncertainty regarding the local structure and dynamics of LiBH4, especially in the high-temperature phase. LiBH4 is an orthorhombic crystal (space group Pnma) at ambient temperature and pressure and is known to undergo a phase transition at around 380 K, but the crystal structure of the high-temperature phase and local dynamics of hydrogen, boron and lithium in this phase was subject to debate. In order to shed more light on the local dynamics of the BH4- unit, as well as the Li ion dynamics, in both the low and high-temperature phases of LiBH4, in this work, we propose to concurrently employ neutron Compton scattering (NCS), neutron transmission (NT), and neutron diffraction (ND) on VESUVIO spectrometer.