Electrochemical impedance spectroscopy error analysis and round robin on dummy cells and lithium-ion-batteries

Moertelmaier

Ragulskis

et al. 2023

Batteries & Supercaps

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A 7 kWh automotive battery module with 396 interconnected cells was tested with electrochemical impedance spectroscopy (EIS) and time-domain pulsing over 260 charge-discharge cycles. An EIS calibration workflow was developed for low complex impedance values in a frequency range of 1 kHz to 50 mHz. Significant corrections on the resistance and the reactance were obtained from the calibration, particularly at frequencies above 100 Hz. Equivalent circuit parameters were extracted from the EIS spectra and the pulse response and investigated with respect to the cycle number and state-ofcharge (SoC). Fit parameters were robustly extracted including R sol , R ct , and L from EIS, and R 0 , τ 1 and τ 2 from time-domain pulsing. The ohmic resistance decreased over the cycling number indicating an enhanced wetting of the electrodes. Charge transfer resistance R ct showed a monotonic increase over the cycles related to cell ageing. From the charge and discharge pulses, the ohmic resistance R 0 was determined from the instantaneous voltage step of the recovery pulse, while the two time constants τ 1 and τ 2 correspond to the slower exponential recovery phase. R 0 from the time-domain showed a similar trend as R sol plus a contribution of R ct from EIS. Overall, we show that calibrated EIS and time-domain pulsing are efficient methods to gain insights into the electrochemical processes related to different SoCs and the cycling ageing of battery modules and packs.

Section: Methodsmentioning

confidence: 99%

Section: Module Eis Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Calibrated Electrochemical Impedance Spectroscopy and Time‐Domain Measurements of a 7 kWh Automotive Lithium‐Ion Battery Module with 396 Cylindrical Cells

Moertelmaier

Ragulskis

et al. 2023

Batteries & Supercaps

Self Cite

“…While these error sources can also be addressed in the uncertainty model framework, we did not include a quantitative analysis in this work, and in particular the calibration standards' uncertainty will be subject to an upcoming study. An overview of the various error sources and their estimated magnitude in error contribution for battery EIS can be found in a recent study [24].…”

mentioning

confidence: 99%

Measurement Uncertainty in Battery Electrochemical Impedance Spectroscopy

Moradpour

IEEE Trans. Instrum. Meas.

Hoffmann

et al. 2022

Self Cite

Electrochemical impedance spectroscopy (EIS) is a widely used method for battery tests in manufacturing and automotive field applications. As such, accurate measurement of the impedance over a broad frequency spectrum is of high relevance, also requiring specific calibration methods and evaluation of error bounds. Here, we report for the first time a comprehensive uncertainty analysis of calibrated EIS for batteries. We aim to identify two uncertainty sources, the fixture repeatability and measurement noise, and evaluate their effect on the measured impedances. To this end, an error model assigned to each of them and the real and imaginary parts of the model parameters are characterized in the frequency range of 100 mHz-5 kHz by performing specific impedance measurements on a shunt resistor and a short standard. We demonstrate how different uncertainties are combined with the measured impedances, incorporating also the impedance calibration procedure. The errors are propagated through the calibration and correction functions by applying the linear error propagation method provided by the UncLib package from METAS. The error bounds are derived from uncertainty propagation in the shunt standard and the prismatic battery cell EIS and verified by conducting a series of measurements. Thereby, the uncertainty is shown as ellipsoids in every frequency point of the Nyquist plot. For instance, at 1 Hz, the 34-Ah prismatic cell shows a calibrated real-part impedance and two standard deviation error bounds of 1.07 m ± 26 μ.

Quantitative Cell Classification Based on Calibrated Impedance Spectroscopy and Metrological Uncertainty

Moradpour

Kienberger

2023

Batteries & Supercaps

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Electrochemical impedance spectroscopy (EIS) is widely used for battery cell testing in industrial production and R&D labs. This work addresses the use of EIS calibration and uncertainty analysis in cell classification. Five scenarios are investigated to discuss qualitatively the impact of calibration and uncertainty on classification. For an experimental demonstration, a cylindrical cell was measured with two mechanical fixtures of different qualities and characterized regarding random errors and calibrated impedances. The impact of uncertainty and impedance calibration on the cell classification is shown, and based on the uncertainty and corresponding error bounds, a confidence level was established for the classification results. Quantitative uncertainty bounds are presented for the full EIS frequency spectrum ranging from 150 mHz to 5 kHz.