65066 2025 eng lecture 0 -- -- -- Sodium-ion batteries (SIBs) have recently gained significant attention as a cost-effective and sustainable alternative to lithium-ion batteries for large-scale energy storage applications and battery-electric vehicles. With their ability to be fully discharged to 0 V, they allow much safer handling and transport. The reversibility of such a complete discharge is, however, debated as the solid electrolyte interphase (SEI) formed by commonly used electrolytes in SIBs becomes unstable at low full-cell voltages. In the present study, the effects of overdischarging SIBs and the implications on their long-term impedance degradation are investigated for commercial SIB-cells, comprising sodium nickel manganese iron oxide (NaNi0.33Mn0.33Fe0.33O2) as cathode active material. During the study, extensive characterization measurements (e.g., electrochemical impedance spectroscopy, open-circuit voltage analysis, etc.) were performed at various stages of degradation. This allows the monitoring of the electrochemical characteristics of the tested SIBs. Notably, the long-term degradation behavior of the cells was significantly affected, indicating lasting changes in the passivating properties of the altered SEI. Finally, the results show that overdischarging can indeed cause irreversible changes in sodium-ion batteries, emphasizing the need to enhance their stability at low full-cell voltages to make the best possible use of their potential safety features. SBS6 – International Sodium Battery Symposium Dresden, Germany 03.09.2025 04.09.2025 0 publish false true Robert Leonhardt eng uncontrolled Overdischarge of sodium ion batteries eng uncontrolled Solid electrolyte interphase eng uncontrolled Impedance spectroscopy eng uncontrolled Battery degradation and aging Angewandte Physik 3 Gefahrgutumschließungen; Energiespeicher 3.1 Sicherheit von Gefahrgutverpackungen und Batterien Energie Elektrische Energiespeicher und -umwandlung Datei im Netzwerk der BAM verfügbar ("Closed Access") Präsentation