Lithiation Behavior of Individual Carbon-Coated Fe3O4 Nanowire Observed by in Situ TEM

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• 作者：Qingmei SuShixin Wang ; Yanling Xiao ; Libing Yao ; Gaohui Du ; Huiqun Ye ; Yunzhang Fang
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：February 16, 2017
• 年：2017
• 卷：121
• 期：6
• 页码：3295-3303
• 全文大小：627K
• ISSN：1932-7455

文摘

Fe₃O₄ nanowires, as a typical transition-metal oxide (TMO), are being considered as promising anodes for lithium ion batteries (LIBs) due to their 1D structure and high specific capacity. However, their underlying mechanism and electrochemical behaviors are still poorly understood. Here, the dynamic behavior and the electrochemical reaction of the carbon-coated Fe₃O₄ (Fe₃O₄@C) nanowire have been investigated directly through assembling a nanoscale LIBs inside transmission electron microscope (TEM). The in situ TEM results reveal that the Fe₃O₄ nanowires undergo cracking and fracturing upon the first lithiation, but the carbon coatings still embrace the oxide cores well after lithiation and play a role in maintaining the mechanical and electrical integrity. Meanwhile the lithiation process involves the conversion of Fe₃O₄ nanowires to Fe nanograins and the formation of Li₂O along the lithium ions diffusion direction. The delithiated product is FeO rather than the original phase of Fe₃O₄ after the first delithiation process. This irreversible phase conversion may be a major cause of capacity fading of the electrode in the first cycle. As for the Fe₃O₄ electrode, about 78% of the capacity loss can be attributed to the irreversible phase reaction in the first cycle. During the subsequent lithiation-delithiation cycles, the Fe₃O₄ electrode shows a reversible conversion between Fe and FeO nanograins, accounting for the good reversibility of Fe₃O₄ anodes for LIBs. Our in situ results provide important insights into the electrochemical behavior and conversion mechanism of TMO-based anodes in LIBs and are helpful for designing LIBs with outstanding performance.