Toward Higher Energy Density All‐Solid‐State Batteries by Production of Freestanding Thin Solid Sulfidic Electrolyte Membranes in a Roll‐to‐Roll Process

All‐solid‐state batteries (SSB) 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. In this work, thin and flexible sulfide solid electrolyte membranes are fabricated and laminated onto a non‐woven fabric using a scalable and solvent‐free, continuous roll‐to‐roll process (DRYtraec). 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. By tuning the thickness, densified membranes with thicknesses ranging from 40 to 160 µm are obtained after a compression step. The resulting SE membranes retain a high ionic conductivity (1.6 mS cm-1) at room temperature. An excellent rate capability is demonstrated in a SSB pouch cell with a Li2O-ZrO2‐coated LiNi0.9C0.05Mn0.05O2 cathode, a 55 µm thin SE membrane, and a columnar silicon anode fabricated by a scalable physical vapor deposition process. At stack level, a promising energy density of 673 Wh L-1(and specific energy of 247 Wh kg-1) is achieved, showcasing the potential for high energy densities by reducing the SE membrane thickness while retaining good mechanical properties.