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 ma terial. 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-ra y powder diffraction analysis showed that the SVO materials lose cryst allinity over the range 0 < x < 1.2, with the simultaneous formation o f elemental silver. In addition, the c lattice parameter for the sampl es decreased linearly from 7.56 to 6.55 Angstrom over the range of 0 < x < 3.3, indicating significant structural changes in the lithiated m aterial. DSC and resistivity measurements also suggested structural ch anges in these products. The oxidation states of the vanadium and silv er components were assigned on the basis of chemical: analysis and X-r ay powder diffraction results and were consistent with the results of FT-IR and room-temperature magnetic susceptibility measurements. Volta mmetry of Li/SVO cells displayed multiple, waves, which correlated wit h the results of the physical characterization studies. These experime nts indicated that the reduction of SVO in lithium batteries can produ ce mixed-valent materials, with the presence of vanadium(V), -(IV) and -(III) possible in the same sample.