Evidence of reversible oxygen participation in anomalously high capacity Li- and Mn-rich cathodes for Li-ion batteries
Evidence of reversible oxygen participation in anomalously high capacity Li- and Mn-rich cathodes for Li-ion batteries
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DOI：
10.1016/j.nanoen.2015.12.027
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发表时间：
2016-03-01
期刊：
影响因子：
17.6
通讯作者：
Yoon, Won-Sub
中科院分区：
文献类型：
--
作者：
Muhammad, Shoaib;Kim, Hyunchul;Yoon, Won-Sub
在原子水平上研究了高容量富锂富锰金属氧化物0.4Li(2)MnO(3)-0.6 limn (0.5)Ni(0.5)O(2)的反应机理。利用高分辨率同步加速器x射线粉末衍射（HRPD）和x射线吸收光谱（XAS）分别对电化学充放电反应的局部和整体结构变化以及过渡金属离子氧化态的变化进行了评价。镍k边吸收光谱表明镍参与了可逆氧化还原反应，而锰k边吸收光谱表明锰离子不参与电化学反应。充电和放电过程中氧占用的Rietveld细化提供了宿主结构可逆氧释放和再容纳的证据；这种独特的氧参与可能是这些电极异常高容量的主要原因。HRPD数据还表明，在循环初期，Li2MnO3组分的特征峰在充电至4.7 V时消失，但在放电至2.5 V时重新出现，符合可逆的锂氧萃取过程。该结果为高容量、富含锂和锰的电极材料在电化学循环时发生的电荷补偿机制提供了新的见解，这是目前文献中激烈争论的话题。(C) 2016年Elsevier Ltd.出版
The reaction mechanism of a high capacity lithium- and manganese-rich metal oxide, 0.4Li(2)MnO(3)-0.6LiMn(0.5)Ni(0.5)O(2), has been investigated at the atomic level. High-resolution synchrotron X-ray powder diffraction (HRPD) and X-ray absorption spectroscopy (XAS) were used, respectively, to evaluate the electrochemical charge and discharge reactions in terms of local and bulk structural changes, and variations in the oxidation states of the transition metal ions. Ni K-edge XAS data indicate the participation of nickel in reversible redox reactions, whereas Mn K-edge absorption spectra show that the manganese ions do not participate in the electrochemical reactions. Rietveld refinements of the oxygen occupancy during charge and discharge provide evidence of reversible oxygen release and re accommodation by the host structure; this unique oxygen participation is likely the main reason for the anomalously high capacity of these electrodes. The HRPD data also show that during the early cycles, characteristic peaks of the Li2MnO3 component disappear when charged to 4.7 V, but reappear on discharge to 2.5 V, consistent with a reversible lithium and oxygen extraction process. The results provide new insights into the charge compensation mechanisms that occur when high capacity, lithium- and manganese-rich electrode materials are electrochemically cycled - a topic that is currently being hotly debated in the literature. (C) 2016 Published by Elsevier Ltd.