Core loss spectroscopies can provide powerful element-specific insight into the redox processes occurring in Li-ion battery cathodes, but this requires an accurate interpretation of the spectral features. Here, we systematically interpret oxygen K-edge core loss spectra of layered lithium transition-metal (TM) oxides (LiMO₂, where M = Co, Ni, Mn) from first principles using density-functional theory (DFT). Spectra are simulated using three exchange–correlation functionals, comprising the generalized gradient approximation (GGA) functional PBE, the DFT–PBE + Hubbard U method, and the meta-GGA functional rSCAN. In general, rSCAN provides a better match to experimentally observed excitation energies of spectral features compared to both PBE and PBE + U, especially at energies close to the main edge. Projected density of states of core-hole calculations show that the O orbitals are better described by rSCAN. Hybridization, structural distortions, chemical composition, and magnetism significantly influence the spectra. The O K-edge spectrum of LiNiO₂ obtained using rSCAN shows a closer match to the experimental X-ray absorption spectroscopy (XAS) when derived from a simulation cell which includes a Jahn–Teller distortion, showing that the DFT-calculated pre-edge feature contains information about not only chemical species but also geometric distortion. Core loss spectra derived from DFT can also differentiate between materials with the same structure and magnetic configuration but comprising different TMs; these differences are comparable to those observed in experimental XAS from the same materials. This foundational work helps establish the extent to which DFT can be used to bridge the interpretation gap between experimental spectroscopic signatures and ab initio methods describing complex battery materials, such as lithium nickel manganese cobalt oxides.

中文翻译：

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层状锂离子电池正极材料氧 K 边 X 射线吸收光谱的原子解释


磁芯损耗光谱可以深入了解锂离子电池阴极中发生的氧化还原过程，但需要准确解释光谱特征。在这里，我们使用密度泛函理论 （DFT） 从第一性原理系统地解释了层状锂过渡金属 （TM） 氧化物（LiMO₂，其中 M = Co、Ni、Mn）的氧 K 边缘磁芯损耗光谱。使用三个交换相关泛函模拟光谱，包括广义梯度近似 （GGA） 函数 PBE、DFT-PBE + Hubbard U 方法和元 GGA 泛函 rSCAN。一般来说，与 PBE 和 PBE + U 相比，rSCAN 与实验观察到的光谱特征激发能量的匹配性更好，尤其是在靠近主边缘的能量处。芯孔计算的投影状态密度表明，rSCAN 可以更好地描述 O 轨道。杂化、结构扭曲、化学成分和磁性会显著影响光谱。当从包含 Jahn-Teller 畸变的模拟单元中得出时，使用 rSCAN 获得的 LiNiO₂ 的 O K 边缘光谱与实验 X 射线吸收光谱 （XAS） 更接近，这表明 DFT 计算的预边缘特征不仅包含有关化学物质的信息，还包含有关几何畸变的信息。从 DFT 得出的磁芯损耗谱也可以区分具有相同结构和磁性构型但包含不同 TM 的材料;这些差异与在相同材料的实验 XAS 中观察到的差异相当。 这项基础工作有助于确定 DFT 在多大程度上可用于弥合实验光谱特征与描述复杂电池材料（如锂镍锰钴氧化物）的从头开始方法之间的解释差距。