Investigation of Li-LixV2O5 Rechargeable Batteries at Different Charged States Using NMR Spectroscopy

Li rechargeable cells made with structural arrangement Li/membrane/ LixV2O5 were examined under three states using NMR spectroscopy; these states are charged, discharged, and over-cycled. 7Li NMR signals at chemical shifts of 0 ppm and around -20 ppm from the resonance frequency, which corresponds to the Li ions from the residual electrolyte at the cathode surface and inside the cathode material of LixV2O5, respectively, were obtained from LixV2O5 samples in both charged and discharged cells. From nuclear spin-lattice relaxation time (T1) measurements, two components due to the Li ions in the electrode surface region and inside the bulk of LixV2O5 particles were obtained from charged cell. The 51V NMR spectra were virtually identical for LixV2O5 from the charged and over-cycled cells; however, the intensity of 51V NMR signal from the discharged cell was significantly lower due to paramagnetic V+4 and V+3 species.