Excessive sodiation and desodiation of commercial NFM-hard carbon sodium-ion batteries induced by low-rate cycling

Title data

Rüther, Tom ; Kinberger, Andrea ; Feistel, Niklas ; Bianchini, Matteo ; Danzer, Michael A.:
Excessive sodiation and desodiation of commercial NFM-hard carbon sodium-ion batteries induced by low-rate cycling.
In: Journal of Power Sources Advances. Vol. 37 (2026) . - 100199.
ISSN 2666-2485
DOI: https://doi.org/10.1016/j.powera.2025.100199

Official URL:

Abstract in another language

Experiments reveal that the electrodes of a commercial NFM hard carbon sodium-ion battery undergo excessive sodiation and desodiation at low charge and discharge rates. These effects are observed during cycling, despite operating strictly within the manufacturer’s recommended voltage limits of 1.5 V to 4.1 V. The resulting increase in charge capacity originates from an additional phase transition in the cathode active material, which manifests itself electrochemically as a voltage plateau that delays reaching the cut-off voltage during charging. The occurrence of the phase transition at high cell voltages is verified by operando X-ray diffraction measurements. During the subsequent discharge, the reverse transition takes place. Unusual deep discharge is enabled by the combination of low overpotentials and the characteristic potential profile of the cell. These phenomena are reproducibly observed across multiple test sequences. To separate the effects of the individual electrodes on this full cell behavior, harvested electrodes from a commercial cell are assembled into an experimental three-electrode setup and analyzed by differential voltage analysis. Since the high-voltage phase transition is reported to involve irreversible processes, adapting characterization and cycling protocols (especially voltage limits) may improve long-term performance and facilitate future analyses.

Further data

Item Type:	Article in a journal
Refereed:	Yes
Keywords:	Commercial cell; Electrode balancing; Hard carbon; Nickel iron manganese oxide; Sodium-ion batteries
Institutions of the University:	Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Lehrstuhl Anorganische Aktivmaterialien für elektrochemische Energiespeicher > Lehrstuhl Anorganische Aktivmaterialien für elektrochemische Energiespeicher - Univ.-Prof. Dr. Matteo Bianchini Faculties > Faculty of Engineering Science > Chair Electrical Energy Systems > Chair Electrical Energy Systems - Univ.-Prof. Dr.-Ing. Michael Danzer Research Institutions > Central research institutes > Bayerisches Zentrum für Batterietechnik - BayBatt
Result of work at the UBT:	Yes
DDC Subjects:	500 Science > 540 Chemistry 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited:	24 Feb 2026 08:33
Last Modified:	24 Feb 2026 08:33
URI:	https://eref.uni-bayreuth.de/id/eprint/96378