Revealing the electrochemical conversion mechanism of porous Co3O4 nanoplates in lithium ion battery by in situ transmission electron microscopy
Revealing the electrochemical conversion mechanism of porous Co3O4 nanoplates in lithium ion battery by in situ transmission electron microscopy
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原位透射电子显微镜揭示多孔Co3O4纳米片在锂离子电池中的电化学转化机理
DOI：
10.1016/j.nanoen.2014.08.006
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发表时间：
2014-10-01
期刊：
影响因子：
17.6
通讯作者：
Du, Gaohui
中科院分区：
文献类型：
--
作者：
Su, Qingmei;Zhang, Jun;Du, Gaohui
近年来，Co3O4纳米结构作为锂离子电池负极材料引起了人们极大的关注。然而，它们的电化学过程和基本机制仍不清楚。本文报道了用原位电子显微镜直接观察多孔Co3O4纳米板/石墨烯在LiBS中的动力学行为和转化机理。用电子衍射和电子能量损失谱分析了锂/脱锂电极的微观结构。结果表明，在第一次锂化过程中，晶型良好的Co3O4转变为许多嵌入在Li2O基质中的Co纳米颗粒。随后的电化学充放电过程被发现是Co纳米颗粒和CoO纳米颗粒之间的可逆相变，这与以前认识的机理不同(即Co和Co3O4之间的可逆转化)。Co3O4纳米板内部的气孔可以容纳体积的膨胀，有利于电极的稳定性，从而提高电化学性能。原位透射电子显微镜显示的不可逆性与半电池测量进一步关联，这可以很好地解释第一个循环的容量损失。(C)2014爱思唯尔有限公司。保留所有权利。
Co3O4 nanostructures have attracted tremendous attention as anode materials for lithium ion batteries (LIBs) recently. However, their electrochemical processes and fundamental mechanism remain unclear. In this paper, we report the direct observation of the dynamic behaviors and the conversion mechanism of porous Co3O4 nanoplates/graphene in LIBs by in situ transmission electron microscopy (TEM). The microstructures of the lithiated/delithiated electrode are analyzed by electron diffraction and electron energy-loss spectroscopy. It is revealed that well-crystalline Co3O4 transform into many Co nanograins embedded in Li2O matrix during the first lithiation. The subsequent electrochemical charge-discharge processes are found to be a reversible phase transition between Co nanograins and CoO nanograins, which is different from the previously recognized mechanism (namely a reversible conversion between Co and Co3O4). Pores within the Co3O4 nanoplates can accommodate the volume expansion, and benefit for the stability of electrode and thus the electrochemical performance. The irreversibility revealed by in situ TEM is further correlated with the half cell measurement, which can well explain the capacity loss in the first cycle. (C) 2014 Elsevier Ltd. All rights reserved.