The lithium sulfur (Li-S) cell chemistry is promising due to the high specific capacity of its active materials resulting in high specific energy cells. Consequently, this battery type is notably suitable for lightweight applications such as aviation. Sulfurized polyacrylonitrile (SPAN) is one of the currently highly prominent materials offering the advantages of the active material sulfur with the absence of dissolved polysulfides. Polysulfides are known to cause the so-called shuttle effect usually resulting in a rapid capacity decrease due to electrolyte depletion and corrosion reactions at the Li anode surface. Owing to the comparably low active material content (around 40 %) in SPAN, optimization (e.g. densification) on electrode level is a crucial aspect for maximizing energy density on cell level. In the project SulForFlight, industrially produced SPAN material is used as active material for manufacturing Li-S batteries. Herby, the scalable production of electrodes as well as their mechanical properties were investigated. Densification of the electrodes and the effects of this process were tested showing improvement potential.
In this work, the optimization of the electrode behavior after compacting was investigated by varying the binder- and conductive additive systems. Additionally, two electrolyte systems were investigated regarding their rate capability and cycling stability. For characterization, optical and mechanical measurements were conducted as well as electrochemical tests using coin cells and multi-layered pouch cells. Recent electrodes achieved discharge capacities up to 530 mAh/g(SPAN) and high rate capabilities up to 3C even after a densification of 50 %. One of the electrode systems has enabled multi-layered pouch cells to run for more than 200 cycles at 1C. Both results are demonstrating the potential for usage in aviation applications.