Preparation Of High Purity V₂O₅ And Its Application In Vanadium Batteries

All vanadium redox flow battery?referred to as vanadium battery?is an efficient and clean storage battery,which has a charge and discharge speed,long life,low costs,no pollution and so on.Electrolyte as the active material of vanadium batteries,responsible for the storage and transmission of energy.some impurity ions in electrolyte will greatly reduce the efficiency of battery and its service life.High purity V₂O₅ is the main raw material for the preparation of vanadium battery electrolyte,but its preparation process is complicated,the preparation cost is high,which restricts the development of vanadium battery.In order to reduce the production cost of high purity V₂O₅ and improve the performance of vanadium electrolyte,the preparation of high purity V₂O₅ and its application in vanadium battery were studied systematically.The main study contents as follows:Firstly,V₂O₅ was prepared by chemical agent?CaCl2 ? MgCl2 ? Al2?SO4?3?removal impurity and vanadium precipitated by hydrolysis removal impurity with industrial grade ammonium vanadium,and VOSO4 electrolyte prepared by that purity V₂O₅.The purity and chemical composition of V₂O₅,the yield of vanaduim,the electrochemical performance of the electrolyte and charge-discharge performance of the battery were tested and analyzed.The result of research show that the purity of V₂O₅ which prepared by the purification process of hydrolysis removal was 99.86 %,the content of K,Na,Si,P,Fe,Mn,Ca,Al was reduced to less than 0.001% and the content of Cr was reduced to 0.008% in the V₂O₅.The electrolyte prepared by the V₂O₅,the electrochemical activity of the electrolyte and the capacity of charge-discharge and efficiency of the battery are improved obviously,compared with not puritied electrolyte and those of electrolyte puritied by the chemical removal agent.Secondly,the conditions of vanadium precipitated by hydrolysis?conditions of vanadium precipitated by hydrolysis,conditions of vanadium precipitated by ammonium salt,conditions of NH4VO3 washing?were studied.High purity V₂O₅ prepared by three kinds of industrial grade ammonium vanadate with different purity under the optimum experimental conditions.The results show that the purity of V₂O₅ is more than 99.9% under the optimum conditions,the actual yield?including transfer loss?of vanadium is above 94%,the content of Cr in V₂O₅ is reduced below 0.004%,the content of K,Na,Si,P,Fe,Mn,Ca,Al is less than0.001%.At last,The VOSO4 electrolyte prepared by the high purity V₂O₅ which prepared under the above optimal experimental conditions with three kinds of materials.The electrochemical performance of the electrolyte and the charge and discharge performance of the battery were studied.The results of cyclic voltammetry showed that the peak current ratio of the three kinds of puritied electrolyte decreased by 21.6%,18.7% and 29.4%,the peak current difference?Rct?decreased by 41.5%,24.5% and 59% respectively compared with the not purified electrolytes.The results of AC impedance showed that the reaction impedance?Rct?of the three kinds of electrolyte decreased by 41.5%,24.5%,59% respectively compared with the not purified electrolytes.The results of the battery charge-discharge study showed that the charge and discharge capacity of battery increased by about 100%,9%,19%,the coulomb efficiency and energy efficiency of battery increased by 1% to 3% compared with the not purified electrolytes.