7Li NMR and 35Cl, 81Br NQR Study of Lithium Ion Conductor LiAlX4 (X = Cl and Br)

The dynamic behavior of LiAlX4 (X = Cl and Br) was studied by means of 7Li NMR and 35Cl, 81Br NQR spectroscopies. The motional narrowing processes of the 7Li NMR due to Li+ diffusion were observed above room temperature for single crystals of LiAlX4. The activation energies for these processes were 43.4 and 42.1 kJ mol−1 for the chloride and bromide analogs, respectively. A stepwise decrease in the 7Li NMR quadrupole splitting suggested that the Li nucleus sees time averaged electric field gradient (EFG) arising from several different sites. The modulation effect of Li+ diffusion on the NQR relaxation times was detected only for LiAlBr4 but not for the chloride analog.