Sustainable Protein‐Based Binder for Lithium‐Sulfur Cathodes Processed by a Solvent‐Free Dry‐Coating Method

In the market for next‐generation energy storage, lithium‐sulfur (Li−S) technology is one of the most promising candidates due to its high theoretical specific energy and cost‐efficient ubiquitous active materials. In this study, this cell system was combined with a cost‐efficient sustainable solvent‐free electrode dry‐coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)‐based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li−S batteries, a renewable, biodegradable, and fluorine‐free polypeptide was employed as a binder for solvent‐free electrode manufacturing. The yielded sulfur/carbon dry‐film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state‐of‐the‐art 1,2‐dimethoxyethane/1,3‐dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide‐solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained.