Variance-based Characterization of Impedance and OCV in 200 Lithium-Ion Cells

Angerpointner L, Mathes J, Shega E, Ringel L, Lehner S (2026)

Publication Language: English

Publication Type: Conference contribution, Abstract of a poster

Publication year: 2026

Event location: Münster DE

Abstract

The cell impedance and open-circuit voltage (OCV) are key parameters besides capacity for assessing the state of health and lifespan of lithium-ion cells. Variations in these parameters reflect the quality of the manufacturing process, while sufficiently large dataset can also identify outliers. Early detection of such outliers is particularly important for future cell-to-pack concepts, where individual cells are practically non-replaceable and the associated risks and costs of failures are significant. This study focuses on the quasi-open-circuit voltage (qOCV) and impedance measurements of 200 brand-new commercial cylindrical 21700 cells (new cells). Established models are applied to analyze the variance in the measurement results. Additionally, eight representative cells (referred to as reference cells) were selected for a more detailed analysis of their impedance across the full state of charge (SoC) range at several selected temperature levels. Impedance was measured using the multi-sine electrochemical impedance spectroscopy (EIS). Measurements for all new cells were conducted at an OCV of 3.6V and a constant temperature of 25 °C. The results were then divided into frequency bands based on variance to identify relevant points of interest (POI) in the frequency spectrum. The reference cells were further characterized across the entire SoC range in 1% increments at 6 temperature levels. To account for these dependencies, an analysis of the variance across SoC and temperature was performed. The qOCV measurement were carried out for all cells with a precision better than 20µV and 100nA across the full SoC range. The variance of these results was analyzed, and specific POIs were identified and correlated with the impedance variance characteristics, as well as with the initial capacity, weight, and initial voltage of the cells.


Authors with CRIS profile

Leonhard Angerpointner Lehrstuhl für Elektrochemische und Elektrische Energietechnologien Jonas Mathes Lehrstuhl für Elektrochemische und Elektrische Energietechnologien Susanne Lehner Lehrstuhl für Elektrochemische und Elektrische Energietechnologien

How to cite

APA:

Angerpointner, L., Mathes, J., Shega, E., Ringel, L., & Lehner, S. (2026, April). Variance-based Characterization of Impedance and OCV in 200 Lithium-Ion Cells. Poster presentation at Advanced Battery Power, Münster, DE.

MLA:

Angerpointner, Leonhard, et al. "Variance-based Characterization of Impedance and OCV in 200 Lithium-Ion Cells." Presented at Advanced Battery Power, Münster 2026.

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