Microwave-Assisted Synthesis of Silver Vanadium Phosphorus Oxide, Ag2VO2PO4: Crystallite Size Control and Impact on Electrochemistry

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• 作者：Jianping Huang ; Amy C. Marschilok ; Esther S. Takeuchi ; Kenneth J. Takeuchi
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：April 12, 2016
• 年：2016
• 卷：28
• 期：7
• 页码：2191-2199
• 全文大小：656K
• 年卷期：0
• ISSN：1520-5002

文摘

Silver vanadium phosphorus oxide, Ag₂VO₂PO₄, is a promising cathode material for Li batteries due in part to its large capacity and high current capability. Herein, a new synthesis of Ag₂VO₂PO₄ based on microwave heating is presented, where the reaction time is reduced by approximately 100× relative to other reported methods, and the crystallite size is controlled via synthesis temperature, showing a linear correlation of crystallite size with temperature. Notably, under galvanostatic reduction, the Ag₂VO₂PO₄ sample with the smallest crystallite size delivers the highest capacity and shows the highest loaded voltage. Further, pulse discharge tests show a significant resistance decrease during the initial discharge coincident with the formation of Ag metal. Thus, the magnitude of the resistance decrease observed during pulse tests depends on the Ag₂VO₂PO₄ crystallite size, with the largest resistance decrease observed for the smallest crystallite size. Additional electrochemical measurements indicate a quasi-reversible redox reaction involving Li⁺ insertion/deinsertion, with capacity fade due to structural changes associated with the discharge/charge process. In summary, this work demonstrates a faster synthetic approach for bimetallic polyanionic materials which also provides the opportunity for tuning of electrochemical properties through control of material physical properties such as crystallite size.