Understanding the High Capacity of Li2FeSiO4: In Situ XRD/XANES Study Combined with First-Principles Calculations

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• 作者：Dongping Lv ; Jingyu Bai ; Peng Zhang ; Shunqing Wu ; Yixiao Li ; Wen Wen ; Zheng Jiang ; Jinxiao Mi ; Zizhong Zhu ; Yong Yang
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：May 28, 2013
• 年：2013
• 卷：25
• 期：10
• 页码：2014-2020
• 全文大小：427K
• 年卷期：v.25,no.10(May 28, 2013)
• ISSN：1520-5002

文摘

The electrochemical mechanism of the cathode material Li₂FeSiO₄ with reversible extraction/insertion of more than one Li⁺ from/into the structure has been studied by techniques of in situ synchrotron X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD). These advanced techniques provide effective solutions to address the limitations of characterization by traditional ex situ methods. The study of in situ Fe K-edge XANES indicates that the Fe ion in the Li₂FeSiO₄ is oxidized continuously to high valence during the charging process from open circuit potential to 4.8 V, which contributes to the high reversible capacities of the materials. In situ XRD and theoretical study from first-principles calculations have been employed to reveal the structural evolution of the Li₂FeSiO₄ underlying the high capacity during the charge/discharge process. The results of both experimental and theoretical studies are consistent and indicate that Li₂FeSiO₄ undergoes two two-phase reactions when the electrode is charged to a high voltage of 4.8 V.

Keywords:

lithium-ion battery; orthosilicate; cathode; synchrotron; electrochemistry; mechanism study; first principles calculation