The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative, hydrogen is widely regarded as a key element for a potential energy solution. However, hydrogen storage is one of the main constraint. Solid state hydrogen storage is a potential alternative to address this problem. Tetrahydroborates are interesting materials for hydrogen storage because of their high gravimetric and volumetric hydrogen capacity, e.g. LiBH4: 18.3 wt. % H2 and 122.5 kg/m3 H2. However, those tetrahydroborates stable at room temperature release hydrogen under thermal input only at high temperatures and present extremely harsh re-hydrogenation conditions. Neutron spectroscopy is a powerful tool to improve this promising hydride materials.