Electrochemical Impedance Spectrum of a Lithium–Sulfur–Bis(Trifluoromethane)Sulfonimide Lithium Salt System: Modeling and Analysis of the Temperature Dependence

Abstract

Background . Lithium sulfur current sources are the most promising modern power sources. But their widespread application is limited by valid methods of troubleshooting of the formation of poorly soluble film on the electrode, and on the separator surfaces. O bjective . The purpose of this paper is to apply the method of electrochemical impedance spectroscopy (EIS) for diagnosis of the parameters impacting on the electrochemical properties of Li–S current sources. M ethods . The study and modeling of the electrochemical impedance spectra of the Li–S elements with LiTFSI in tetraethylene glycol dimethyl ether electrolyte is carried out. The calculated method of the capacitance change and analysis of the mechanisms of electrochemical processes with using of the EIS method are performed. R esults . It is determined that the using of several calculated methods and models of the EIS spectra can not only diagnose the condition of the degree of discharge and temperature in the Li–S current sources, but also enables to correct the quantitative composition of the electrolyte and cathode mass. Conclusions. The paper describes the methods of calculation EIS spectra for analyzing the impact of the Li–S current sources component composition and structural characteristics on their status. The regions of the spectrum, responsible for the various processes implementation were identified in the studied electrochemical systems. This has created the possibility to establish the particular appearance of the charge effect when heated elements discharged due to an increasing of the sulfur nano-sized particles number as a result of the discharge process in the cathode space.