Crown‐Shell‐Core Synergistic Ion‐Conduction Strategy via Tailored Solvation Structure for Dendrite‐Free Lithium Metal Battery

Designing functional fillers with more accessible Lewis acid sites to regulate the solvation structure is key to developing high‐performance polyethylene oxide (PEO) solid electrolytes, while the enlarged filler/matrix interfaces inevitably lead to compromised Li + transport kinetics. Herein, a “crown‐shell‐core” multi‐dimensional synergistic ion‐conduction strategy of PEO‐based solid‐state electrolytes (SSEs) is designed to regulate solvation structure and improve the interfacial compatibility of filler/matrix, which is induced by ionic‐liquid (Li‐IL) impregnated bimetallic UIO‐66(Zr/Hf) (BUIO) (Li‐IL@BUIO, denoted as BUIL) filler. The introduction of structural defects generates abundant open metal sites, serving as Lewis acidic “crowns” capable of immobilizing anions and weakening EO‐Li coordination. The filler with a 3D open framework acts as a host, while the ionic liquid is encapsulated into the pores, forming nanowetted interfaces and rapid Li + transport channels within the core. The PEO‐Li‐IL@BUIO/Cellulose (PIBU/CL) exhibits a high Li + transference number (0.682), high Li + conductivity (5.83 × 10 −4 S cm −1 , 30°C), and a wide electrochemical window up to 4.9 V. The PIBU/CL also demonstrates excellent compatibility and long‐term stability with lithium metal. Impressively, the LFP | PIBU/CL | Li cells deliver an extended cycling life of over 800 cycles at 0.5 C with a Coulombic efficiency of 99.8%.