Comprehensive electrochemical impedance spectroscopy study of Si-Based anodes using distribution of relaxation times analysis

Silicon (Si) and Silicon Monoxide (SiO) have been considered as anode materials for the next-generation Li-ion batteries (LiBs) based on their high energy density. A combination of electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis is used to investigate the electrochemical behaviors of Si and SiO anodes. Systematic DRT analysis on EIS data collected using different cell geometries (e.g., half and symmetrical cells) allows to deconvolute the origins of individual polarization losses and their evolutions under different operating conditions such as temperature and state-of-charge (SOC). Predominant polarization losses were found to be contact impedance, solid-electrolyte interphase (SEI) layer related impedance, and charge transfer impedance based on calculated activation energy and time constant that are comparable with literature. The impedance behavior of Si and SiO showed unique patterns during cycling, which could be explained by the changes in SEI due to the presence of cracks according to previous experimental studies. In addition, the fitted SEI and charge transfer resistance of Si show larger variation than those of SiO at a given SOC. Recommendations for SOC operating range in commercial applications are given for Si and SiO to achieve the best electrode performance.