A Gradient Nanodomain High-Entropy Polymer Electrolyte Tape for Pressure-Free Solid-State Lithium Batteries

High-entropy polymer electrolytes (HEPE) have attracted significant attention owing to their exceptional design flexibility in properties and thin-film processability. However, building high-performance HEPE with well controlled nanodomains of multi-components remains a critical challenge due to serious microphase separation. Here, we report a tri-phase high-entropy polymer electrolyte (HEPE) tape featuring ultrafine soft-rigid gradient nanodomains approaching the single-chain length scale, to achieve notable simultaneous enhancements in mechanical, electrochemical, and interfacial properties. The HEPE is realized through Li⁺-bond-regulated nanophase separation of polyethylene oxide (PEO), poly (methyl methacrylate) (PMMA), and polyvinylidene fluoride-co-hexafluoropropylene (PVFH), leading to high-entropy microstructures at the levels of chain conformation and phase domains. Consequently, the HEPE exhibits a high room-temperature ionic conductivity of 0.24 mS∙cm^-1, exceptional mechanical properties (strength of 22.1 ± 2.3 MPa, toughness of 87.7 MJ∙m^-3, elastic recovery of 66.7%), and interfacial adhesion toughness of 325 ± 15 N∙m^-2. Benefitting from these properties, the HEPE can generate physico-electrochemical synergistic effects on stabilizing the lithium metal anode with a long cycling life of 750 h at 0.1 mA∙cm^-2. The resultant solid-state Li|HEPE|NCM811 cell delivers a high capacity of 205.5 mAh∙g^-1 even without stack pressure. This study indicates a promising high-entropy tri-component mixing strategy for the design and fabrication of HEPEs.