Effect of Major Impurity in the Vanadium-Rich Solution on the Growth of NaV2O5 Crystals under Hydrothermal Conditions

NaV₂O₅ is a promising cathode material for ion batteries with high capacity and good cycle performance. The high concentration of vanadium and low impurity in vanadium-rich solution makes it possible to be used as raw material for vanadium product preparation. Vanadium solution containing impurity was prepared to investigate its influence mechanism on NaV₂O₅ crystal precipitation. The influence of four major impurity elements on the precipitation of NaV₂O₅ following the order of P > Al > Si > Fe. With the increase of impurity concentrations, vanadium conversion rate and V content of the precipitates decreased to varying degrees, while impurity content increased. When concentrations of Fe, Al and Si were high, the resulting precipitate was still NaV₂O₅, but the crystal structure changed. The AlOH and SiOH hider the condensation between VOH and broke the rod into irregular flakes and blocks. As P concentration gradually increased, the precipitates changed from NaV₂O₅ to VO₂(H₂O) 0.5 and then to Na₃.053((V₅O₉)(PO₄)2(OH)0.1(H₂O)8, meanwhile, the morphologies changed from rod to plate, then to cross-like, and finally to cube. Revealing the influence of impurity in vanadium-rich solution on the growth of NaV₂O₅ crystal is conducive to the popularization of the process.