原子单位
材料科学
阴极
分析化学(期刊)
无机化学
物理化学
化学
物理
色谱法
量子力学
作者
Xing Li,Kangjia Zhang,David Mitlin,Eunsu Paek,Mingshan Wang,Fei Jiang,Yun Huang,Zhenzhong Yang,Yue Gong,Lin Gu,Wengao Zhao,Yingge Du,Jianming Zheng
出处
期刊:Small
[Wiley]
日期:2018-09-09
卷期号:14 (40)
被引量:40
标识
DOI:10.1002/smll.201802570
摘要
Lithium-rich Li[Li1/6 Fe1/6 Ni1/6 Mn1/2 ]O2 (0.4Li2 MnO3 -0.6LiFe1/3 Ni1/3 Mn1/3 O2 , LFNMO) is a new member of the xLi2 MnO3 ·(1 - x)LiMO2 family of high capacity-high voltage lithium-ion battery (LIB) cathodes. Unfortunately, it suffers from the severe degradation during cycling both in terms of reversible capacity and operating voltage. Here, the corresponding degradation occurring in LFNMO at an atomic scale has been documented for the first time, using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), as well as tracing the elemental crossover to the Li metal anode using X-ray photoelectron spectroscopy (XPS). It is also demonstrated that a cobalt phosphate surface treatment significantly boosts LFNMO cycling stability and rate capability. Due to cycling, the unmodified LFNMO undergoes extensive elemental dissolution (especially Mn) and O loss, forming Kirkendall-type voids. The associated structural degradation is from the as-synthesized R-3m layered structure to a disordered rock-salt phase. Prior to cycling, the cobalt phosphate coating is epitaxial, sharing the crystallography of the parent material. During cycling, a 2-3 nm thick disordered Co-rich rock-salt structure is formed as the outer shell, while the bulk material retains R-3m crystallography. These combined cathode-anode findings significantly advance the microstructural design principles for next-generation Li-rich cathode materials and coatings.
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