7Li NMR and two-dimensional exchange study of lithium dynamics in monoclinic Li3V2(PO4)3

High-resolution solid-state Li-7 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 assi ned 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.