Determination of Lithium Insertion Sites in LixTiP4 (x = 2-11) by Electron Energy-Loss Spectroscopy

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• 作者：Vincent Mauchamp ; Philippe Moreau ; Laure Monconduit ; Marie-Liesse Doublet ; Florent Boucher ; Guy Ouvrard
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：March 15, 2007
• 年：2007
• 卷：111
• 期：10
• 页码：3996 - 4002
• 全文大小：379K
• 年卷期：v.111,no.10(March 15, 2007)
• ISSN：1932-7455

文摘

A combined computational and experimental study of the electron energy-loss near edge structures forLi_xTiP₄ at the lithium K edge is presented. Li_xTiP₄ is considered to be a possible negative electrode materialfor lithium batteries. The complex behavior of this compound during lithium insertion/extraction was studiedusing first-principles simulations of the fine structures in electron energy-loss spectra (EELS) and band structurecalculations. These calculations were performed with the WIEN2k code, within the density functional theoryand were compared to experimental spectra obtained for the following lithium compositions (x = 2, 4.3, 5.5,9, 11). This study brings to light the existence of spectroscopic features characteristic of lithium atoms insertedin tetrahedral sites of the TiP₄ matrix. These sites are shown to be preferred with respect to octahedral onesfor low lithium compositions. The spectroscopic differences between the electrodes formed through oxidationor reduction processes allowed us to discriminate between two different electrochemical pathways in chargeand discharge: a biphasic process is involved in charge (oxidation), whereas a solid solution occurs in discharge(reduction). This study demonstrates the sensitivity of the Li K edge to these two different behaviors.