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

ABSTRACT 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.