Ni‐rich layered oxides (NRLO) are widely considered among the most promising cathode materials for high energy‐density lithium ion batteries. However, the high proportion of Ni content accelerates the cycling degradation that restricts their large‐scale applications. The origins of degradation are indeed heterogeneous and thus there are tremendous efforts devoted to understanding the underlying mechanisms at multi‐length scales spanning atom/lattice, particle, porous electrode, solid‐electrolyte interface, and cell levels and mitigating the degradation of the NRLO. This review combines various advanced in situ/ex situ analysis techniques developed for resolving NRLO degradation at multi‐length scales and aims to convey a comprehensive picture of its heterogeneous degradation mechanism. This contribution starts with discussing various factors influencing NRLO stability and proceeds to elaborate the multi‐scale characterization, including synchrotron‐based X‐ray diffraction, X‐ray absorption spectroscopy, X‐ray imaging, Raman spectroscopy, electron microscopy, online‐electrochemical mass spectrometry, and secondary ion mass spectrometry. Further, the detailed degradation mechanisms at each length scale are analyzed, and corresponding strategies to alleviate the degradation are evaluated. By conveying the progress (mainly between the years 2015 and 2020), methods, insights, and perspectives, this review contributes significantly to the understanding and tackling of the cycling degradation of NRLO.

中文翻译：

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探索并解决多长度尺度上富镍层状氧化物阴极的非均质降解

富镍层状氧化物（NRLO）被广泛认为是高能量密度锂离子电池最有希望的正极材料。但是，高含量的镍会加速循环降解，从而限制了其大规模应用。降解的根源确实是异质的，因此需要付出巨大的努力来理解跨越原子/晶格，颗粒，多孔电极，固体电解质界面和细胞水平的多长度尺度的潜在机制，并减轻NRLO的降解。这篇综述结合了为解决多长度尺度的NRLO降解而开发的各种先进的原位/异位分析技术，旨在全面介绍其异质降解机理。这项贡献从讨论影响NRLO稳定性的各种因素开始，然后阐述了多尺度表征，包括基于同步加速器的X射线衍射，X射线吸收光谱，X射线成像，拉曼光谱，电子显微镜，在线电化学质量质谱和二次离子质谱。此外，分析了每种长度尺度下的详细降解机理，并评估了缓解降解的相应策略。通过传达进展情况（主要是在2015年至2020年之间），方法，见解和观点，本综述对理解和解决NRLO的循环降解有重要贡献。X射线吸收光谱，X射线成像，拉曼光谱，电子显微镜，在线电化学质谱和二次离子质谱。此外，分析了每种长度尺度下的详细降解机理，并评估了缓解降解的相应策略。通过传达进展情况（主要是在2015年至2020年之间），方法，见解和观点，本综述对理解和解决NRLO的循环降解有重要贡献。X射线吸收光谱，X射线成像，拉曼光谱，电子显微镜，在线电化学质谱和二次离子质谱。此外，分析了每种长度尺度下的详细降解机理，并评估了减轻降解的相应策略。通过传达进展情况（主要是在2015年至2020年之间），方法，见解和观点，本综述对理解和解决NRLO的循环降解做出了重要贡献。