Molecular Engineering of Metal–Organic Frameworks to Synergistically Enhance Bulk‐Interfaces Ion Kinetics for Quasi‐Solid‐State Lithium Metal Batteries

Abstract Quasi‐solid‐state electrolytes (QSSEs) represent a promising strategy to address the interfacial incompatibility of inorganic solid electrolytes and the sluggish ion kinetics of polymer solid electrolytes. Conventional approaches employ porous matrices to host minimal liquid electrolytes, yet remain constrained by limited ion transport enhancement and neglected electrode–electrolyte interfacial dynamics, resulting in poor electrochemical performance under high‐rate and high‐loading conditions. Hence, this work develops a novel quasi‐solid electrolyte through molecular engineering of metal–organic frameworks (UiO‐66‐Br electrolyte), which modulates Li⁺‐TFSI − interactions to establish solvent‐separated ion pairs (SSIPs)‐dominated solvation structures. This yields a high ionic conductivity of 1.58 mS cm −1 at 20 °C. Furthermore, the derived LiBr/LiF‐rich solid‐electrolyte interphase (SEI) enables ultrafast interfacial ion transport kinetics. Through synergistic promotion of bulk‐interfaces ion transport kinetics, while the LFP|UiO‐66‐Br|Li cells demonstrate exceptional cycling stability, achieving ≈100% capacity retention after 2300 cycles at 5 C with negligible decay. Under high mass‐loading conditions (>20 mg cm −2 ), which can maintain 95.1% capacity retention over 100 cycles. This molecular engineering strategy pioneers a new paradigm for designing high‐performance quasi‐solid‐state lithium‐metal batteries.