Polar–Nonpolar Synergistic Terpolymer Enables Ultra‐Thin Sulfide‐Based Membrane for High‐Energy‐Density and Low‐Cost All‐Solid‐State Batteries

ABSTRACT For developing high‐energy‐density all‐solid‐state sulfide batteries (ASSBs), large‐area sulfide electrolyte films produced via wet processes hold great potential. However, it is still a major obstacle in the wet process of sulfide membranes to find suitable polymer binders with excellent (electro)chemical compatibility and bonding properties. Here, we not only employ a terpolymer adhesive (Poly(ethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate)) with polar–nonpolar synergistic effects to facilitate the wet‐process manufacture of sulfide‐based films, but also adopt a sulfide electrolyte prepared without expensive Li 2 S to reduce raw material costs. The sulfide‐based electrolyte film (terP‐SF) features an ultra‐thin thickness (32 µm), favorable mechanical properties, and high ionic conductivity (1.32 mS/cm). For electrochemical performance, the terP‐SF has fast ion transport kinetics and electrical insulation, which enables the NCM83//terP‐SF//In‐Li battery to deliver high‐rate performance and long‐term cycling stability (with a capacity retention rate of approximately 76.6% after 600 cycles). Furthermore, given the cost‐effectiveness of scaled‐up production of ASSB, a pouch cell configured as NCM83//terP‐SF//Si with an energy density of 320.4 Wh/kg and volumetric energy of 710.7 Wh/L is successfully assembled. This work inspires the selection of binders in wet‐process film formation and further guides the resolution of engineering and scientific challenges in the commercialization of high‐energy‐density and low‐cost ASSBs.