Structural Behavior of Li₂B₁₀H₁₀

On the basis of X-ray and neutron powder diffraction, first-principles calculations, and neutron vibrational spectroscopy, Li₂B₁₀H₁₀ was found to exhibit atypical hexagonal symmetry to best stabilize the ionic packing of the relatively small Li⁺ cations and large ellipsoidal B₁₀H₁₀^2– anions. Moreover, differential scanning calorimetry and neutron-elastic-scattering fixed-window scans suggested that Li₂B₁₀H₁₀, similar to its polyhedral cousin Li₂B₁₂H₁₂, undergoes an order–disorder phase transition near 640 K. These results provide valuable structural information pertinent to understanding the potential role that Li₂B₁₀H₁₀ plays during LiBH₄ dehydrogenation–rehydrogenation as well as its prospects as a superionic Li⁺ cation conductor.