Identification of an Unconventional Zinc Coordination Site in Anhydrous ZnxV2O5 Aerogels from X-ray Absorption Spectroscopy

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• 作者：Marco Giorgetti ; Stefano Passerini ; William H. Smyrl ; and Mario Berrettoni
• 刊名：Chemistry of Materials
• 出版年：1999
• 出版时间：August 1999
• 年：1999
• 卷：11
• 期：8
• 页码：2257 - 2264
• 全文大小：122K
• 年卷期：v.11,no.8(August 1999)
• ISSN：1520-5002

文摘

V₂O₅ aerogel (ARG) has been studied as an insertion host for lithium ions and for severalpolyvalent cations. The stability, reversibility, and capacity for ion insertion and releaseprocesses make the amorphous ARG an interesting material for battery applications. Thelocal structural modifications resulting from the chemical insertion of Zn²⁺ ions into thehost have been investigated by X-ray absorption spectroscopy (XAS). X-ray absorption near-edge structure (XANES) spectra at the V K-edge of Zn_xV₂O₅ did not shown any substantivechange as a function of increasing amounts of intercalated ions, thus indicating the absenceof interactions between the intercalated ions and the vanadium ions. To study the structuralsites of the polyvalent ions, EXAFS (extended X-ray absorption fine structure) spectra havebeen recorded at the Zn K-edge. The EXAFS analysis showed that the Zn²⁺ ions are 4-foldcoordinated by almost coplanar oxygens. In addition, differences in the first shell of theinserted Zn²⁺ as a function of the intercalation level have been observed. The first-shellZn-O bond length shortened and the EXAFS Debye-Waller factor increased. This suggestsa decrease of the local geometrical order of the first shell as polyvalent cations are inserted.