Fast Li diffusion in crystalline LiBH4 due to reduced dimensionality: Frequency-dependent NMR spectroscopy

摘要: The hexagonal and orthorhombic form of lithium borohydride, ${\text{LiBH}}_{4}$, are investigated by temperature frequency-dependent nuclear magnetic resonance (NMR) spectroscopy. local electronic structure microscopic diffusion parameters determined recording both $^{6,7}\text{L}\text{i}$ NMR spectra spin-lattice relaxation (SLR) rates. rates the high-temperature flank SLR-NMR peaks ${\text{LiBH}}_{4}$ clearly depend on frequency which unequivocally reveals a low-dimensional process. Due to very limited number suitable model substances this makes borohydride an extremely attractive material study effect reduced dimensionality Li dynamics. Most likely, spatial confinement hopping is also responsible for high ionic conductivity found polymorph, recently.