Investigation of the Sodium Ion Pathway and Cathode Behavior in Na3V2(PO4)2F3 Combined via a First Principles Calculation

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• 作者：Weixin Song ; Xiaoyu Cao ; Zhengping Wu ; Jun Chen ; Yirong Zhu ; Hongshuai Hou ; Qing Lan ; Xiaobo Ji
• 刊名：Langmuir
• 出版年：2014
• 出版时间：October 21, 2014
• 年：2014
• 卷：30
• 期：41
• 页码：12438-12446
• 全文大小：610K
• ISSN：1520-5827

文摘

The electrochemical properties of Na₃V₂(PO₄)₂F₃ cathode utilized in the sodium ion battery are investigated, and the ion migration mechanisms are proposed as combined via the first principles calculations. Two different Na sites, namely, the Na(1) and Na(2) sites, could cause two sodium ions of Na₃V₂(PO₄)₂F₃ to be extracted or inserted by a two-step electrochemical process accompanied by structural reorganization that could be responsible for the redox reaction of V^3+/4+. Because the calculated average voltage (V_avg) of the second charging plateau is 4.04 V for the optimized system but 4.38 V for the unoptimized one, the reorganization of the cathode system can make a stable configuration and lower the extraction energy. Three designed pathways for sodium ions along the x, y, z directions in Na₃V₂(PO₄)₂F₃, known as a 3D ions transport tunnel, have activation energies (E_a) of 0.449, 0.2, and 0.323 eV, respectively, by using DFT calculations, demonstrating the different feasibilities of the migration directions.