Fluorination-Decoupling MOFs for Enhanced Solvation Dynamics and Interface Stability in Lithium Metal Batteries

Persistent interfacial instability remains a critical bottleneck for solid-state lithium metal batteries, necessitating electrolyte designs that simultaneously regulate bulk transport and interfacial reactions. A fluorination-decoupling strategy is proposed by integrating fluorinated metal-organic frameworks (MOFs) with Lewis-acidic sites into PVDF-HFP quasi-solid-state electrolytes to tailor Li⁺ solvation dynamics and induce robust interfacial protection. Experimental results confirmed that the electron‑withdrawing and sterically bulky fluorinated moieties disrupted the metal-oxygen coordination environment and enhanced the Lewis acidity of the MOF. These modifications limited anion mobility, promoted ion‑pair dissociation, and weakened Li⁺ coordination. Moreover, preferential interactions with fluorosilane facilitated the formation of a solid electrolyte interphase rich in LiF without compromising bulk conductivity (1.16 × 10^-3 S cm^-1 at 30 °C). These mechanistic insights translated into outstanding cycling stability: Li||Li symmetric cells operated stably for over 2200 h at 0.2 mA cm^-2, while Li||LiFePO₄ and Li||NCM811 retained 93.5% and 70.0% capacity after 2000 and 450 cycles at 20C and 5C, respectively. This study provides a new avenue to tailor Li⁺ solvation and improves interfacial stability in solid-state electrolytes by precise control of fluorine-framework interactions.