An Unchoked High‐Entropy Composite Electrolyte With Li ⁺ ‐Bond Enabled Tough‐and‐Adhesive Nano‐Interpenetrating Network

Abstract Polymer/ceramic composite electrolytes are expected to integrate the advantages of both polymeric and ceramic electrolytes. However, this attractive potential has long been blocked by a highly‐resistive polymer/ceramic interface that hinders the Li ⁺ migration inside. To conquer this challenge, here, a conceptual design and fabrication of a high‐entropy composite electrolyte (HECE) is reported to build a robust Li ⁺ ‐migration‐friendly polymer/ceramic interface, which brings significant enhancement in ion‐conduction and overall mechanical properties. To do that, the Li ⁺ ‐ionic bond has been harnessed to realize a tough‐and‐adhesive polymer matrix featured by high‐entropy nano‐interpenetrating network (nano‐IPN). The resultant HECE exhibits high ionic conductivity (0.42 mS cm ⁻¹ ) at room temperature, high Li ⁺ ‐transference number (0.86), and superior mechanical strengths (7.1 MPa for tensile and 3.7 gf µm ⁻¹ for puncture). Benefitting from the HECE, the overall electrochemical performances of the solid‐state lithium‐metal‐batteries are greatly improved compared with their low‐entropy counterparts, indicating the significant merits of the high‐entropy design in facilitating Li ⁺ ‐conduction kinetics, stabilizing ion deposition, and suppressing lithium dendrite formation. This study indicates the promise of high‐entropy polymeric microstructures for the design and fabrication of high‐performance composite electrolytes.