Chemical State and Quantitative Analysis of Transition Metals in NCM Cathode Materials Based on X-ray Photoelectron Spectroscopy:Challenges and Solutions
X-ray photoelectron spectroscopy(XPS)plays an important role in the analysis of lithium nickel cobalt manganese oxide(LiNixCoyMn1-x-yO2,NCM)cathode materials for lithium-ion batteries.However,the overlap of the main peaks and Auger peaks of Ni,Co,and Mn transition metals in NCM makes it difficult to identify and quantitatively analyze the chemical states of these three elements.In this study,taking LiNi0.8Co0.1Mn0.1O2(NCM811)as an example,the interference between the main peaks and Auger peaks of transition metals in the XPS spectra was analyzed,and an algorithm based on nonlinear least squares fitting was proposed to fit the overlapping 2p peaks of transition metal.By comparing different chemical states of Ni,Co and Mn reference samples,Ni(OH)2,NiOOH,LiCoO2 and MnO2 were selected as the fitting reference spectra.Compared to the conventional Gaussian/Lorentzian fitting method,the fitting method proposed in this study does not require manual adjustment of fitting parameters,making the XPS spectral fitting process independent of the operator and improving repeatability.The effective application of this nonlinear least squares fitting method in XPS spectrum analysis of NCM811 cathode materials has be confirmed in this study.The main peaks of transition metals are separated from the Auger peaks of other elements.It provides a reference solution for the difficult problem of chemical state identification and quantitative analysis of the overlap between the main peaks and Auger peaks of Ni,Co and Mn transition metals.
lithium-ion batterieslithium nickel cobalt manganese oxideXPSnonlinear least squares fitting
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