Analysis of 3.4 Ah lithium-sulfur pouch cells by electrochemical impedance spectroscopy

Despite great progress in lithium-sulfur (Li-S) batteries, the electrochemical reactions in the cell are not yet fully understood. Electrode processes, complex interfaces and internal resistance may be characterized by electrochemical impedance spectroscopy (EIS). EIS is a non-destructive technique and easy to apply, though there are challenges in ensuring the reproducibility of measurements and the interpretation of impedance data. Here, we present the impedance behavior of a 3.4 Ah Li-S pouch cell characterized by EIS. The impedance changes were analyzed over the entire depth-of-discharge, depth-of-charge, and at various temperatures. Based on the formation of intermediates during (dis)charging, the changes of resistances are observed. Overall, the increase in temperature causes a decrease in electrolyte viscosity, lowering the surface energy which can improve the penetration of the electrolyte into the electrode pores. Moreover, the effect of superimposed AC current during EIS measurement was analyzed, and the results show the dependence of the charge transfer resistance on superimposed AC current which was lower compared to steady-state conditions and consents with theory. (c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

This study characterizes the impedance behavior of lithium-sulfur batteries using electrochemical impedance spectroscopy (EIS) and investigates the effects of temperature and superimposed AC current on impedance. The results provide insights into the electrochemical reactions and resistance changes in lithium-sulfur batteries.