Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 16: Energy Storage Materials and Devices II

CPP 16.4: Talk

Monday, March 9, 2026, 18:15–18:30, ZEU/0260

X-Ray Absorption Near-Edge and Photoemission Spectroscopy of Deintercalation and Redox Reactions in Alluaudite-Type Na-Ion Cathodes — •Neama Imam¹, Karsten Henkel¹, Stephan Werner², Christoph Pratsch², Anna Milewska³, Janina Molenda³, Jan Ingo Flege¹, and Ehrenfried Zschech¹ — ¹Brandenburg University of Technology Cottbus - Senftenberg, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie, BESSY II, Germany — ³AGH University of Science and Technology, Krakow, Poland

We have investigated alluaudite-type Na_2.5−xFe_1.75(SO₄)₃ cathodes that exhibit a three-dimensional open-channel framework with multiple Na sites. Using spatially resolved X-ray absorption near-edge spectroscopy (XANES), performed within a transmission X-ray microscope (TXM), and lab-based X-ray photoelectron spectroscopy (XPS), we have examined Na⁺ deintercalation and Fe²⁺/Fe³⁺ charge compensation at different selected charging states. This combination of bulk- and surface-sensitive methods allows correlating Na⁺ depletion with Fe³⁺ formation, potentially identifying nanoscale redox heterogeneities and tracking changes in the local Na chemical environment. Our study builds on a broader investigation [1] that includes theoretical calculations as well as structural and electrochemical analyses.

[1] J. Molenda et al., Acta Mater. 301, 121582 (2025).

Keywords: Na-ion batteries; Na deintercalation; Fe redox; spectromicroscopy; XPS