An Advanced Impedance Analysis for Interfacial Reaction of Sulfide-Based Solid-State Batteries in Rapid Cycling

Interfacial features are primary factors of the overall electrochemical performance in solid-state electrochemical devices. They mainly influence ionic resistance as well as electronic conduction depending on their shape and distribution. So far, researches have been focused on strengthening the interfacial structure by various architecturing methods (e.g., multiscale structuring, core-shell coating, micropatterning) to enhance the mechanical stability and increase energy density. Furthermore, analytical approaches to demonstrate this enhancement in interfacial structure are also gaining interest.<br/>Electrochemical impedance spectroscopy (EIS) with the conventional fitting approach for Nyquist plot has mostly been utilized for quantitative investigation of each electrochemical response in electrodes and electrolytes without damaging cells. However, as the complexity of the cell’s electrochemical reaction rises, so does the degree of freedom in circuit layout, which limits the precision of the measurement of individual resistance components.<br/>In this study, we suggest an advanced analysis tool based on the distribution of relaxation times (DRT) method to accurately determine the electrochemical components of the complicated solid-state interfacial properties in sulfide-based solid-state batteries. Based on the advanced approach, we constructed precise equivalent circuit for the composite cathode of solid-state batteries. It also confirmed that the conventional fitting approach overestimated one of the electrode resistance by 40%, and identified the new resistance component from the lithium depletion layer. Finally, we validated that our results are in good agreement with the computational methods, and we established that this method is appropriate for quantitatively analyzing complicated interfacial reactions in solid-state batteries.