High Ionic Conductive, Mechanical Robust Sulfide Solid Electrolyte Films and Interface Design for All‐Solid‐State Lithium Metal Batteries

Abstract All‐solid‐state lithium batteries (ASSLBs) are considered a promising technology for next‐generation energy storage systems due to their inherent safety. However, the conventional laboratory‐scale ASSLBs reported to date are based on pellet‐type structures with thick solid electrolyte layers, leading to challenges related to low energy densities and poor electrochemical performance. In this study, porous adhesive poly(ethylene vinyl acetate) (PEVA) scaffolds and polytetrafluoroethylene (PTFE) binders are utilized to interweave sulfide solid electrolytes into freestanding films with an ultra‐low thickness of 40 µm, high ionic conductivity of 1.1 mS cm −1 , and a high tensile strength of 74 MPa. To mitigate the reduction reaction between the PTFE binder and the lithium metal anode, a Li 3 N‐rich solid electrolyte interphase (SEI) in situ on lithium metal is formed, and the assembled symmetric cell shows excellent cycling stability within 800 h at the current density of 0.2 mA cm −2 and room temperature. Additionally, the ASSLBs using oxidatively stable Li 2 ZrCl 5 F in the composite cathode and the prepared solid electrolyte film demonstrate exceptional cycling performance and fast‐charging capability, with a high cell‐level energy density of 354.4 Wh kg −1 . The ASSLBs prepared by coupling E‐LPSCl film and stable interface design exhibit excellent electrochemical performance and a high cell‐level energy density.