J. Phys. Chem. B, ASAP Article 10.1021/jp057015+ S1520-6106(05)07015-X
Web Release Date: March 17, 2006
7Li NMR and Two-Dimensional Exchange Study of Lithium Dynamics in Monoclinic Li3V2(PO4)3
L. S. Cahill, R. P. Chapman, J. F. Britten, and G. R. Goward*
Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street W., Hamilton, ON, L8S 4M1 Canada
High-resolution solid-state 7Li NMR was used to characterize the structure and dynamics of lithium ion transport in monoclinic Li3V2(PO4)3. Under fast magic-angle spinning (MAS) conditions (25 kHz), three resonances are clearly resolved and assigned to the three unique crystallographic sites. This assignment is based on the Fermi-contact delocalization interaction between the unpaired d-electrons at the vanadium centers and the lithium ions. One-dimensional variable-temperature NMR and two-dimensional exchange spectroscopy (EXSY) are used to probe Li mobility between the three sites. Very fast exchange, on the microsecond time scale, was observed for the Li hopping processes. Activation energies are determined and correlated to structural properties including interatomic Li distances and Li-O bottleneck sizes.