Mechanistic Insights into the Cycling Behavior of Sulfur Dry‐Film Cathodes

Abstract

AbstractAll‐solid‐state lithium–sulfur batteries (ASSB‐LiS batteries) are considered among advanced candidates for next‐generation energy storage systems, as they break with restrictions and limitations that liquid electrolytes impose on lithium‐ion batteries and lithium‐sulfur batteries (LiS‐batteries), meaning enhanced safety and higher energy densities. However, investigations under realistic conditions on pouch cell level are challenging, as it is necessary to implement a scalable preparation method for sheet‐type cathodes with high sulfur utilization and loading. In this study, a solvent‐free process to prepare free‐standing cathode sheets with low binder content down to 0.1 wt% PTFE is demonstrated. The contribution of binder and electrolyte on the conversion reaction of sulfur is discussed. Sheet‐type cathodes reach nearly theoretical sulfur utilization of 1672 mAh gS−1 and outstanding reversible capacity retention with 72% of initial discharge capacity after 400 cycles by adapting cut‐off voltages to the stability window of the electrolyte. Furthermore, an all‐solid‐state pouch cell is demonstrated using the dry‐film cathode, which is successfully tested for 50 cycles at different C‐rates. Thickness monitoring of the cell stack gives fundamental insights into the volume change and breathing behavior of both cathode and anode.