Abstract Quantitative analysis of Ni2+/Ni3+ using X-ray photoelectron spectroscopy (XPS) is important for evaluating the crystal structure and electrochemical performance of Lithium-nickel–cobalt-manganese oxide (Li[NixMnyCoz]O2, NMC). However, quantitative analysis based on Gaussian/Lorentzian (G/L) peak fitting suffers from the challenges of reproducibility and effectiveness. In this study, the Ni2+ and Ni3+ standard samples and a series of NMC samples with different Ni doping levels were synthesized. The Ni2+/Ni3+ ratios in NMC were quantitatively analyzed by non-linear least-squares fitting (NLLSF). Two Ni 2p overall spectra of synthesized Li [Ni0.33Mn0.33Co0.33]O2(NMC111) and bulk LiNiO2 were used as the Ni2+ and Ni3+ reference standards. Compared to G/L peak fitting, the fitting parameters required no adjustment, meaning that the spectral fitting process was free from operator dependence and the reproducibility was improved. Comparison of residual standard deviation (STD) showed that the fitting quality of NLLSF was superior to that of G/L peaks fitting. Overall, these findings confirmed the reproducibility and effectiveness of the NLLSF method in XPS quantitative analysis of Ni2+/Ni3+ ratio in Li[NixMnyCoz]O2 cathode materials.

中文翻译：

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Li[Ni x Mn y Co z ]O 2 阴极材料中Ni 2+ /Ni 3+ 的定量分析：XPS光谱的非线性最小二乘拟合

摘要 使用 X 射线光电子能谱 (XPS) 对 Ni2+/Ni3+ 进行定量分析对于评估锂镍钴锰氧化物 (Li[NixMnyCoz]O2, NMC) 的晶体结构和电化学性能非常重要。然而，基于高斯/洛伦兹 (G/L) 峰拟合的定量分析面临重现性和有效性的挑战。在本研究中，合成了 Ni2+ 和 Ni3+ 标准样品以及一系列具有不同 Ni 掺杂水平的 NMC 样品。NMC 中的 Ni2+/Ni3+ 比率通过非线性最小二乘拟合 (NLLSF) 进行定量分析。合成的 Li [Ni0.33Mn0.33Co0.33]O2(NMC111) 和块状 LiNiO2 的两个 Ni 2p 整体光谱用作 Ni2+ 和 Ni3+ 参考标准。与 G/L 峰拟合相比，拟合参数无需调整，这意味着光谱拟合过程不依赖于操作员，并且提高了再现性。残差标准偏差(STD)的比较表明NLLSF的拟合质量优于G/L峰拟合。总的来说，这些发现证实了 NLLSF 方法在 Li[NixMnyCoz]O2 正极材料中 Ni2+/Ni3+ 比率的 XPS 定量分析中的重现性和有效性。