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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 15: Poster Session I
CPP 15.62: Poster
Montag, 17. März 2025, 19:00–21:00, P4
XPS study of redox mechanism in Na2.5−xFe1.75(SO4)3 cathode material for high-voltage sodium-ion batteries — •Neama Imam1, Karsten Henkel1, Anna Milewska2, Janina Molenda2, Ehrenfried Zschech1, and Jan Ingo Flege1 — 1Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus-Senftenberg, Germany — 2AGH University of Krakow, Faculty of Energy and Fuels, Krakow, Poland
A multiplet splitting model based on the original work by Gupta and Sen has been used to track the redox mechanism and electronic structure of Na2.5−xFe1.75(SO4)3, a high-performance cathode material for sodium-ion batteries (SIBs). This high-purity, off-stoichiometric open-channel cathode material with a tailored sodium-ion distribution, synthesized using an optimized solid-state route, demonstrates a high operating voltage of ∼3.8 V, surpassing the values reported for other cathode materials in the literature. X-ray photoelectron spectroscopy (XPS) was employed to analyze the evolution of the material’s electronic structure at various charging potentials. Fe2p3/2 spectra decomposition using the multiplet splitting model revealed the gradual oxidation of Fe2+ to Fe3+ during battery charging while transitioning from its pristine state (x=0) with the presence of only Fe2+ at the cathode surface to the highest sodium de-intercalation level (x=1.61). This result is consistent with the electrochemical analysis.
Keywords: sodium-ion batteries; polyionic cathode; XPS; multiplet splitting model