Synthetic methods for crystallite size control of bimetallic polyanionic battery compositions

Abstract

Bimetallic polyanionic materials, such as silver vanadium phosphorus oxide (AgVOPO, SVOP), are promising cathode materials for Li batteries due in part to their large capacity and high current capability. A new synthesis of AgVOPObased on microwave heating is disclosed, where the reaction time is reduced by approximately 100 times relative to other reported methods, and the crystallite size is controlled via synthesis temperature, showing a linear positive correlation of crystallite size with temperature. Reaction times of an hour or less are sufficient to render phase-pure material after reaction at 50° C. to 180° C., significantly lower than the temperatures reported for other methods. Crystallite sizes between 42 nm and 60 nm are achieved by the novel method, smaller than by other methods. Silver/vanadium atomic ratios of 1.96 to 2.04 in the as-synthesized SVOP result and appear temperature-dependent. Notably, under galvanostatic reduction, the AgVOPOsample with the smallest crystallite size delivers the highest capacity and shows the highest loaded voltage.