Lithium-Ion Battery Degradation in Grid Applications: Analysis through Frequency- and Time-Domain Parameterization

• Published in: Journal of the Electrochemical Society 2024-12, Vol.171 (12), p.120501
• Main Authors: Ohrelius, Mathilda, Lindström, Rakel Wreland, Lindbergh, Göran
• Format: Article
• Language: English
• Subjects: electrochemical impedance spectroscopy; lithium-ion battery; physics-based model; stationary energy storage
• ISSN: 0013-4651; 1945-7111; 1945-7111
• DOI: 10.1149/1945-7111/ad92db

Lithium-ion batteries have a great potential in stationary energy storage, both for first- and second life, but the understanding and tools to evaluate cell degradation needs to be improved. In this study, the degradation of batteries subjected to three types of stationary services, as well as the repurposing of cells from more demanding to a milder application is investigated. The milder cycle is frequency regulation with a maximum C-rate of 1.5 C (FR 1.5C ) and the more demanding cycles peak shaving with a C-rate of 1 C (PS 1C ) and FR and PS combined (FRPS 2C ). The main driver for accelerated capacity loss was identified as the state-of-charge (SOC) change during operation, increasing the rate of degradation for PS and FRPS. The cell impedance was measured and fitted to a physics-based model to deconvolute the sources of polarization increase. A tortuosity increase in the negative electrode was seen for all cells, as well as a resistance increase. FRPS 2C and PS 1C further showed a decrease in the electrolyte mass transport properties. When repurposed to the milder FR 1.5C application, PS 1C showed a clear decrease in capacity loss rate while more heterogeneous degradation might be the reason for a higher rate of degradation for the repurposed FRPS 2C cell.