Synthesis and electrochemical properties of amorphous vanadates of general formula RVO4 (R = In, Cr, Fe, Al, Y) vs. Li

A method is described for the low-temperature preparation of amorphous vanadates of general formula RVO4 (R = In, Cr, Fe, Al, Y), and their electrochemical properties vs. Li are reported. A dissolution-reprecipitation process from a mixed solution of NH4VO3 and R(NO3)(3) was used to prepare these compounds. By appropriate annealing of the amorphous precursors, several crystallized vanadates were obtained as well. Among all of these vanadates, either amorphous or crystallized, only those with R = In and Fe are of potential interest as negative electrodes in lithium-ion rechargeable batteries since they display reversible capacities as large as 900 mAh/g. This different electrochemical behavior depending on the nature of the metallic element implies that R is not just a spectator with respect to the Li uptake into these materials. From both electrochemical and in situ x-ray diffraction data, a mechanism of Li uptake/removal different from the usual Li insertion/deinsertion process is proposed.