Insights into charge transfer dynamics of Li batteries through temperature-dependent electrochemical impedance spectroscopy (EIS) utilizing symmetric cell configuration

Studying charge transfer processes in Li batteries poses a challenge due to their complicated nature and the battery's inherent inertness. While electrochemical impedance spectroscopy (EIS) offers a promising approach to investigating these processes, its effectiveness is hindered by the complexity of the data generated and the ambiguity in the analyses. Here, we demonstrate that the assignment process is not straightforward for complex secondary Li batteries, and it necessitates additional measurements and in-depth analysis. We first performed simplification of the impedance data by employing symmetric cell configurations to obtain charge transfer resistance values for each electrode. We second took advantage of altering three parameters during the EIS measurement: electrolyte composition, measurement temperature, and the state of health to extract important parameters related to both the anodic and cathodic charge transfer mechanisms. The analysis enabled the correlation of the observed charge transfer resistances to the corresponding electrochemical process and to obtain the kinetic parameters of the studied process. Our work illustrates how EIS can be used to study and understand the intricate electrochemical charge transfer processes in Li batteries, which are difficult to explore using alternative techniques.