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Origin of extra capacity in advanced Li–Rich cathode materials for rechargeable Li–Ion batteries
Chemical Engineering Journal ( IF 15.1 ) Pub Date : 2021-05-13 , DOI: 10.1016/j.cej.2021.130293
Katarzyna Redel , Andrzej Kulka , Katarzyna Walczak , Anna Plewa , Emil Hanc , Mateusz Marzec , Li Lu , Janina Molenda

High-voltage Li-rich oxides are very attractive as cathode materials for Li-ion batteries due to their high energy density and promising specific parameters. In this paper detailed analysis of extra capacity based on the relationship between electrochemical performance and structure evolution of the new stoichiometric Li-Mn-Ni-O group has been discussed. Origin of the extraordinary reversible capacity (~335 mAh∙g−1 at C/20) of Li[Li0.27Mn0.63Ni0.1]O2 was examined with particular emphasis on changes in superstructure cation-ordering in transition metal (TM) layers, TM ions migration as well as oxygen participation during electrochemical processes. The composition, local geometry, chemical states variations of TMs and oxygen at different states of charge were investigated by means of synchrotron-based X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) techniques. Specific structural rearrangements during lithium (de)insertion were examined using operando-XRD, transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and selected area electron diffraction (SAED) investigations. Detailed analysis confirmed highly reversible C2/m → C2/m + R-3 m ↔ C2/m + Fd-3 m phase transitions during charge/discharge mechanisms as well as specific superstructure cation-ordering (Li1/3TM2/3) in TM layer, that could partially vanish reversibly upon delithiation process. In the pristine sample high density of planar defects between neighboring domains was observed towards the [1 0 0], [11-0] and [1 1 0] zone axis.



中文翻译:

用于可充电锂离子电池的高级富锂正极材料额外容量的起源

高压富锂氧化物由于其高能量密度和有希望的特定参数而非常有吸引力,可作为锂离子电池的正极材料。本文基于电化学性能与新型化学计量的Li-Mn-Ni-O基团的结构演化之间的关系,对额外容量进行了详细分析。Li [Li 0.27 Mn 0.63 Ni 0.1 ] O 2的超强可逆容量(在C / 20下约为335  mAh∙g -1)的起源我们特别检查了过渡金属(TM)层中超结构阳离子有序的变化,TM离子迁移以及电化学过程中的氧参与情况。通过基于同步加速器的X射线吸收光谱(XAS)和X射线光电子能谱(XPS)技术研究了在不同电荷状态下TMs和氧的组成,局部几何形状,化学状态变化。使用操作方法检查了锂(去)插入过程中的特定结构重排-XRD,透射电子显微镜(TEM),高角度环形暗场扫描透射电子显微镜(HAADF-STEM)和选定区域电子衍射(SAED)研究。详细的分析证实了在充电/放电过程中C2 / m→C2 / m + R-3 m↔C2 / m + Fd-3 m的高度可逆转变以及特定的上层结构阳离子有序化(Li 1/3 TM 2/3)在TM层中,这可能会在脱锂过程中部分可逆地消失。在原始样品中,在[1  0  0]处观察到相邻畴之间的高密度平面缺陷,[1个1个--0]和[1  1  0]区域轴。

更新日期:2021-05-22
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