Characterization of Lithium Borohydride using Neutron Scattering Techniques

Lithium borohydride, LiBH$_{4}$, is a complex metal hydride that shows great promise as a hydrogen storage medium with a volumetric hydrogen density of 122 kg H/m$^{3}$ and a gravimetric hydrogen density of 18.5 wt. {\%}. While numerous NMR, Raman, and infrared investigations have been reported in the literature, neutron scattering investigations of LiBH$_{4}$ have been limited due to the large neutron absorption cross-section of naturally occurring lithium and boron. We have recently synthesized an isotopically-enriched lithium borohydride, containing $^{7}$Li and $^{11}$B, which eliminates the large neutron absorption cross-section that arises from the presence of $^{6}$Li and $^{10}$B. The results of powder neutron diffraction, inelastic neutron scattering, and quasi-elastic neutron scattering investigations on the $^{7}$Li$^{11}$BH$_{4}$ material are presented. These measurements provide a fundamental understanding of the behavior of hydrogen within lithium borohydride, and they provide a basis to understand changes concomitant with the introduction of catalytic or destabilizing compounds.