LI-7 NMR AND CL-35, BR-81 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 Li-7 NMR. and Cl-35, Br-81 NQR spectroscopies. The motional narrowing processes of the Li-7 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 Li-7 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.