SOLID-STATE CHARACTERIZATION OF REDUCED SILVER VANADIUM-OXIDE FROM THE LI/SVO DISCHARGE REACTION

The reduction of silver vanadium oxide (SVO, AgV2O5.5) by lithium was studied via the solid-state characterization of the reduced cathode material. LixAgV2O5.5 products were isolated over a range of 0 < x < 3.3, with corresponding voltages vs Li ranging from +3.25 to +1.8 V. X-ray powder diffraction analysis showed that the SVO materials lose crystallinity over the range 0 < x < 1.2, with the simultaneous formation of elemental silver. In addition, the c lattice parameter for the samples decreased linearly from 7.56 to 6.55 Angstrom over the range of 0 < x < 3.3, indicating significant structural changes in the lithiated material. DSC and resistivity measurements also suggested structural changes in these products. The oxidation states of the vanadium and silver components were assigned on the basis of chemical: analysis and X-ray powder diffraction results and were consistent with the results of FT-IR and room-temperature magnetic susceptibility measurements. Voltammetry of Li/SVO cells displayed multiple, waves, which correlated with the results of the physical characterization studies. These experiments indicated that the reduction of SVO in lithium batteries can produce mixed-valent materials, with the presence of vanadium(V), -(IV) and -(III) possible in the same sample.