Intermolecular Interaction-Driven Contact Ion Pair-Dominated Solvation Structure Enabling Stable Electrode–Electrolyte Interfaces for Quasi-Solid-State Lithium Metal Batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based polymer electrolytes demonstrate significant potential for quasi-solid-state lithium metal batteries (QSSLMBs) owing to their exceptional room-temperature ionic conductivity. However, the uneven distribution of DMF solvent induces the development of nonuniform solvation structures within electrolytes. Moreover, the different solvation structures exhibit pronounced discrepancies in interfacial stability and ionic transport kinetics, resulting in sluggish ion transport and electrochemically unstable electrode-electrolyte interfaces. Herein, we report precise modulation of the solvation structure through intermolecular interaction between the ZIF-67 filler and the DMF solvent. The corresponding Co-N site in ZIF-67 specifically adsorbs the C═O group of the DMF solvent, driving the formation of a uniform contact ion pair (CIP)-dominated solvation structure, which simultaneously enhances ionic transport kinetics and stabilizes electrode-electrolyte interfaces. The optimized electrolyte endows Li//Li symmetric cells with ultralong cycling stability exceeding 5600 h at 0.1 mA cm⁻², while Li//NCM811 full cells achieve excellent cycling stability for more than 1600 cycles at 4.3 V and 200 cycles at 4.5 V, respectively. This interfacial modulation paradigm provides fundamental guidance for developing high-voltage QSSLMBs (4.5 V) through precise solvation structure engineering.