Key Laboratory of Materials Interface Science and Engineering, Ministry of Education, Taiyuan University of Technology
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DOI:
10.7502/j.issn.1674-3962.2015.05.03
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Abstract:
Transition metal oxides have been used as one of the most promising candidates as anode materials for lithium ion batteries (LIBs). However, their electrochemical process remains unclear. Here we directly observe the dynamic behaviors and conversion mechanism of CuO nanowire in LIBs by in situ transmission electron microscopy. The results show that a reaction front propagates progressively along the nanowire and always keeps a conical shape during the whole process. The conical reaction interface also verifies that lithiation proceeds from the nanowire surface towards its center. After lithiation, the originally straight CuO nanowire became heavily distorted and prolonged. The lithiation process causes an axial elongation of 43.1%, a radial expansion of 40%, and the total volume expansion of 185%. Also, single crystalline CuO nanowires are found to transform to multicrystalline nanowires consisting of many Cu nanograins (2~3 nm) embedded in Li2O matrix. The delithiated product is not CuO but Cu2O, accounting for the irreversible electrochemical process and the large capacity fading of the anode material in the first cycle.