Electrochemical Properties and Sodium-Storage Mechanism of Ag2Mo2O7 as the Anode Material for Sodium-Ion Batteries

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• 作者：Dr. Nan Chen ; Dr. Yu Gao ; Meina Zhang ; Dr. Xing Meng ; Prof. Chunzhong Wang ; Prof. Yingjin Wei ; Dr. Fei Du and Prof. Gang Chen
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：May 17, 2016
• 年：2016
• 卷：22
• 期：21
• 页码：7248-7254
• 全文大小：2192K
• ISSN：1521-3765

文摘

Silver molybdate, Ag₂Mo₂O₇, has been prepared by a conventional solid-state reaction. Its electrochemical properties as an anode material for sodium-ion batteries (SIBs) have been comprehensively examined by means of galvanostatic charge–discharge cycling, cyclic voltammetry, and rate performance measurements. At operating voltages between 3.0 and 0.01 V, the electrode delivered a reversible capacity of nearly 190 mA h g⁻¹ at a current density of 20 mA g⁻¹ after 70 cycles. Ag₂Mo₂O₇ also demonstrated a good rate capability and long-term cycle stability, the capacity reaching almost 100 mA h g⁻¹ at a current density of 500 mA g⁻¹, with a capacity retention of 55 % over 1000 cycles. Moreover, the sodium storage process of Ag₂Mo₂O₇ has been investigated by means of ex situ XRD, Raman spectroscopy, and HRTEM. Interestingly, the anode decomposes into Ag metal and Na₂MoO₄ during the initial discharge process, and then Na⁺ ions are considered to be inserted into/extracted from the Na₂MoO₄ lattice in the subsequent cycles governed by an intercalation/deintercalation mechanism. Ex situ HRTEM images revealed that Ag metal not only remains unchanged during the sodiation/desodiation processes, but is well dispersed throughout the amorphous matrix, thereby greatly improving the electronic conductivity of the working electrode. The “in situ” decomposition behavior of Ag₂Mo₂O₇ is distinct from that of chemically synthesized, metal-nanoparticle-coated electrode materials, and provides strong supplementary insight into the mechanism of such new anode materials for SIBs and may set a precedent for the design of further materials.