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Correlations between Transition-Metal Chemistry, Local Structure, and Global Structure in Li2Ru0.5Mn0.5O3 Investigated in a Wide Voltage Window
Chemistry of Materials ( IF 7.2 ) Pub Date : 2017-11-02 00:00:00 , DOI: 10.1021/acs.chemmater.7b02299
Yingchun Lyu 1, 2 , Enyuan Hu 3 , Dongdong Xiao 1 , Yi Wang 1 , Xiqian Yu 1 , Guiliang Xu 4 , Steven N. Ehrlich 5 , Khalil Amine 4 , Lin Gu 1, 6 , Xiao-Qing Yang 3 , Hong Li 1
Affiliation  

Li2Ru0.5Mn0.5O3, a high capacity lithium-rich layered cathode material for lithium-ion batteries, was subject to comprehensive diagnostic studies, including in situ/ex situ X-ray diffraction, X-ray absorption spectroscopy (XAS), pair distribution function, and high resolution scanning transmission electron microscopy analysis, to understand the correlations between transition-metal chemistry, structure, and lithium storage electrochemical behavior. Ru–Ru dimers were identified in the as-prepared sample and found to be preserved upon prolonged cycling. Presence of these dimers, which are likely caused by the delocalized nature of 4d electrons, is found to favor the stabilization of the structure in a layered phase. The in situ XAS results confirm the participation of oxygen redox into the charge compensation at high charge voltage, and the great flexibility of the covalent bond between Ru and O may provide great reversibility of the global structure despite the significant local distortion around Ru. In contrast, the local distortion around Mn occurs at low discharge voltage and is accompanied by a layered to 1T phase transformation, which is found to be detrimental to the cycle performances. It is clear that the changes of local structure around individual transition-metal cations respond separately and differently to lithium intercalation/deintercalation. Cations with the capability to tolerate the lattice distortion will be beneficial for maintaining the integrality of the crystal structure and therefore is able to enhance the long-term cycling performance of the electrode materials.

中文翻译:

在宽电压窗口中研究Li 2 Ru 0.5 Mn 0.5 O 3中的过渡金属化学,局部结构和整体结构之间的相关性

Li 2 Ru 0.5 Mn 0.5 O 3,是用于锂离子电池的高容量富锂分层阴极材料,已经接受了全面的诊断研究,包括原位/异位X射线衍射,X射线吸收光谱(XAS),对分布函数和高分辨率扫描透射电子显微镜分析,以了解过渡金属化学,结构与锂存储电化学行为之间的相关性。在制备的样品中鉴定出Ru-Ru二聚体,并发现在长时间循环后可以保留。发现这些二聚体的存在可能是由4d电子的离域性质引起的,有助于形成层状相的结构稳定。XAS的原位结果证实了在高充电电压下氧气氧化还原参与了电荷补偿,尽管Ru周围存在明显的局部扭曲,但Ru和O之间的共价键具有很大的灵活性,可能会提供整体结构的可逆性。相反,Mn周围的局部变形在低放电电压下发生,并伴有分层到1T的相变,这对循环性能有害。显然,各个过渡金属阳离子周围的局部结构变化分别对锂嵌入/脱嵌反应有所不同。具有容忍晶格畸变能力的阳离子将有利于保持晶体结构的完整性,因此能够增强电极材料的长期循环性能。
更新日期:2017-11-03
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