A Physical Impedance Model of Lithium Intercalation into Graphite Electrodes for a Coin-Cell Assembly

Graphite electrodes are widely used in commercial metal-ion batteries as anodes. Electrochemical impedance spectroscopy serves as one of the primary non-destructive techniques to obtain key information about various batteries during their operation. However, interpretation of the impedance response of graphite electrodes in contact with common organic electrolytes can be complicated. It is especially challenging, particularly when utilizing the 2-electrode configuration that is common in battery research. In this work, we elaborate on a physical impedance model capable of accurately describing the impedance spectra of a graphite|electrolyte|metallic Li system in a coin-cell assembly during two initial charge/discharge cycles. We analyze the dependencies of the model parameters for graphite and metallic lithium as a function of the state of charge to verify the model. Additionally, we suggest that the double layer capacitance values obtained during specific intercalation stages could help to determine if the area-normalized values align with the expected range. The data and the procedure necessary for calibration are provided. Electrochemical impedance spectroscopy is a sensitive research technique for gaining insights into the underlying mechanisms of battery systems. The authors present a physical impedance model that explains the three-stage mechanism of lithium-ion intercalation into graphite electrodes, using a two-electrode coin cell configuration across two initial lithiation and delithiation cycles. Important electrochemical parameters are provided and validated through these cycles. The results provide valuable insights and can serve as a benchmark for the future research.image

Automated summary

This article presents a physical impedance model that accurately describes the impedance spectra of graphite electrodes in a coin-cell assembly. The model parameters are analyzed to verify its effectiveness. Additionally, the authors propose using double layer capacitance values to determine if the normalized values align with expectations.