The concentration gradient is a strategic design, adjusting the distribution of Ni, typically with a higher Ni content in the core and a higher Mn content toward the surface. This design leverages the pivotal role of the Ni/Mn ratio, seeking to optimize cathode performance by balancing Ni's high capacity with Mn's stabilizing effects, particularly at the surface where degradation commonly occurs during cycling. Our study delves into the intricate structural and chemical transformations within concentration gradient cathode materials during electrochemical cycling. Utilizing advanced synchrotron X-ray techniques, including hard and soft X-ray absorption spectroscopy (hXAS, sXAS), and nanoscale X-ray imaging, we investigate buried changes in concentration gradient LiNiMnCoO (CG NMC622). Contrary to conventional assumptions, our findings challenge the notion that cycling stability relies solely on Mn stability. Unraveling the roles of Ni and Mn, we uncover how their individual and collective contributions impact the cathode's overall performance. This investigation transcends established paradigms, shedding light on the crucial mechanisms governing the enhanced cycling stability of Ni-rich layered cathode materials.

中文翻译：

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了解成分梯度富镍层状 LiNi0.6Mn0.2Co0.2O2 正极材料的循环和热稳定性的改善

浓度梯度是一种策略性设计，可调整镍的分布，通常在核心处具有较高的镍含量，而在表面则具有较高的锰含量。该设计利用了镍/锰比率的关键作用，通过平衡镍的高容量与锰的稳定作用来优化阴极性能，特别是在循环过程中经常发生降解的表面。我们的研究深入研究了电化学循环过程中浓度梯度阴极材料内复杂的结构和化学转变。利用先进的同步加速器 X 射线技术，包括硬 X 射线吸收光谱和软 X 射线吸收光谱（hXAS、sXAS）和纳米级 X 射线成像，我们研究了浓度梯度 LiNiMnCoO (CG NMC622) 的隐藏变化。与传统假设相反，我们的研究结果挑战了循环稳定性仅依赖于锰稳定性的观念。通过阐明镍和锰的作用，我们揭示了它们的单独和集体贡献如何影响阴极的整体性能。这项研究超越了既定的范式，揭示了控制富镍层状正极材料增强循环稳定性的关键机制。