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

An interlaboratory Round-Robin comparison between three-labs is conducted where calibrated electrochemical-impedance-spectroscopy (EIS) is measured on prismatic cell dummies and prismatic batteries. Advanced EIS calibration workflow is employed allowing for precise measurements of low micro-Ohm impedances in a broad frequency range of 50 mHz to 10 kHz. Significant systematic-error corrections are obtained from the calibration. For instance, a correction of the raw data of one order of magnitude is applied for the reactance and more than 100% for the resistance at 1 kHz. Statistical analysis shows very good repeatability for the three-labs. For frequencies up to 100 Hz the differences of the resistance values are below 10 μΩ, while at 10 kHz the differences reach 200 μΩ. The various error sources contributing to EIS are analysed and compared to finite-element-modelling, particularly on the contacting fixture and positional accuracy. Also, a calibrated EIS repeatability study is done at different temperatures providing insights into the electrochemical properties of the battery. In summary, we provide for the first time a comprehensive quantitative analysis of the EIS repeatability and accuracy including different labs. This is relevant for establishing EIS as a tool for quality control in battery production and battery characterization for automotive applications.