New Insight into the Atomic Structure of Electrochemically Delithiated O3-Li(1鈥?i>x)CoO2 (0 鈮?x 鈮?0.5) Nanoparticles

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• 作者：Xia Lu ; Yang Sun ; Zelang Jian ; Xiaoqing He ; Lin Gu ; Yong-Sheng Hu ; Hong Li ; Zhaoxiang Wang ; Wen Chen ; Xiaofeng Duan ; Liquan Chen ; Joachim Maier ; Susumu Tsukimoto ; Yuichi Ikuhara
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：December 12, 2012
• 年：2012
• 卷：12
• 期：12
• 页码：6192-6197
• 全文大小：452K
• 年卷期：v.12,no.12(December 12, 2012)
• ISSN：1530-6992

文摘

Direct observation of delithiated structures of LiCoO₂ at atomic scale has been achieved using spherical aberration-corrected scanning transmission electron microscopy (STEM) with high-angle annular-dark-field (HAADF) and annular-bright-field (ABF) techniques. The ordered Li, Co, and O columns for LiCoO₂ nanoparticles are clearly identified in ABF micrographs. Upon the Li ions extraction from LiCoO₂, the Co-contained (003) planes distort from the bulk to the surface region and the c-axis is expanded significantly. Ordering of lithium ions and lithium vacancies has been observed directly and explained by first-principles simulation. On the basis of HAADF micrographs, it is found that the phase irreversibly changes from O3-type in pristine LiCoO₂ to O1-type Li_xCoO₂ (x 鈮?0.50) after the first electrochemical Li extraction and back to O2-type Li_xCoO₂ (x 鈮?0.93) rather than to O3-stacking after the first electrochemical lithiation. This is the first report of finding O2-Li_xCoO₂ in the phase diagram of O3-LiCoO₂, through which the two previously separated LiCoO₂ phases, i.e. O2 and O3 systems, are connected. These new investigations shed new insight into the lithium storage mechanism in this important cathode material for Li-ion batteries.

Keywords:

LiCoO₂; structural evolution; scanning transmission electron microscopy (STEM); Li-ion batteries