Fabrication and Characterization of Lithium–Sulfur Batteries

Kurzfassung

This work is focused on the characterization of the Li–S battery by application of several characterization techniques under in situ and ex situ conditions. Using X–ray diffraction, the reaction of sulfur was monitored during discharge and charge, and the formation of nano–crystalline lithium sulfide as end product of discharge was identified for the first time in operando. The structural changes of sulfur and its partial amorphization were observed after charge and analyzed using the Rietveld method. Furthermore, electrochemical impedance spectroscopy was applied during cycling to measure the impedance characteristics of the cell. For this, an electrical equivalent circuit was designed to describe specific physical and electrochemical process. Thus, the resistance of the electrolyte, the charge transfer resistance in the electrodes, as well as the reaction and dissolution of isolating products were simulated and quantified. The polysulfides, as well as S8 and Li2S, were investigated in an organic electrolyte using UV–vis spectroscopy. Here, the species S6 2− and S3 •− were identified and semi–quantified at several states of discharge.