Synthesis, Crystal Structure, and Properties of the Alluaudite-Type Vanadates Ag2–xNaxMn2Fe(VO4)3

详细信息    查看全文

• 作者：Hamdi Ben Yahia ; Masahiro Shikano ; Mitsuharu Tabuchi ; Ilias Belharouak
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4643-4649
• 全文大小：402K
• 年卷期：0
• ISSN：1520-510X

文摘

The new members of the Ag_2–xNa_xMn₂Fe(VO₄)₃ (0 ≤ x ≤ 2) solid solution were synthesized by a solid-state reaction route, and their crystal structures were determined from single-crystal X-ray diffraction data. The physical properties were characterized by Mössbauer and electrochemical impedance spectroscopies, galvanostatic cycling, and cyclic voltammetry. These materials crystallize with a monoclinic symmetry (space group C2/c), and the structure is considered to be a new member of the AA′MM′₂(XO₄)₃ alluaudite family. The A, A′, M, and X sites are fully occupied by Ag⁺/Na⁺, Ag⁺/Na⁺, Mn²⁺, and V⁵⁺, respectively, whereas a Mn²⁺/Fe³⁺ mixture is observed in the M′ site. The Mössbauer spectra confirm that iron is trivalent. The impedance measurements indicate that the silver phase is a better conductor than the sodium phase. Furthermore, these phases exhibit ionic conductivities 2 orders of magnitude higher than those of the homologous phosphates. The electrochemical tests prove that Na₂Mn₂Fe(VO₄)₃ is active as positive and negative electrodes in sodium-ion batteries.