All-solid-state batteries (ASSB) show great promise for the advancement of high-energy batteries. To maximize the energy density, a key research interest lies in the development of ultrathin and highly conductive solid electrolyte (SE) layers.

The talk will present how thin and flexible, yet mechanically stabilized, sulfide solid electrolyte membranes can be fabricated by lamination onto a non-woven fabric using a scalable and solvent-free roll-to-roll process. These membranes show significantly improved tensile strength compared to unsupported sheets, which facilitates cell assembly and allows a continuous component production using a single-step calendering process. An excellent rate capability could be demonstrated in an ASSB pouch cell (5 cm²) consisting of a NMC cathode, the SE membrane, and a columnar silicon anode fabricated by a scalable physical vapor deposition process. In the single-layer pouch cell, the SE membrane of 55 µm thickness did not affect the cell performance or lead to short circuits, enabling decreased cost and volume of the separator compared to a common pelletized cell as well as potentially high energy densities.

However, the solvent-free processing of SE powder to films requires a binder. As polytetrafluoroethylene (PTFE) is easily fibrillated, it is currently the most common choice. Unfortunately, PTFE is electrochemically unstable at the low potential on the anode side. Nevertheless, in this work stable long-term cycling (1000+ cycles) and an excellent CE was demonstrated in pouch cells employing a dry processed SE layer containing PTFE, combined with a Si anode. To rationalize this, the second part of the talk will focus on the investigation of electrochemical stability of SE films containing PTFE binder under different anode potentials, highlighting the importance of the SE dry film processing for the battery performance.