Synergistic Effects of Fluorinated Li‐Based Metal‐Organic Framework Filler on Matrix Polarity and Anion Immobilization in Quasi‐Solid State Electrolyte for Lithium‐Metal Batteries

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) based electrolyte is a promising alternative to liquid electrolytes in lithium metal batteries. However, its commercial application is limited by high crystallinity and low Li+ ion conductivity. In this study, we synthesized a fluorinated Li‐based metal‐organic framework (Li‐MOF‐F) and used it as a filler to address these limitations. The strategy for the Li‐MOF‐F filler stands out in two main aspects: framework structure for rapid Li+ ion transport and F‐functional group with electronegativity. The LiO4 with π‐π conjugated dicarboxylate enables the reversible Li intercalation in the lattice structure. The fluorine atoms with electronegativity rearrange polymer matrix from non‐polar to polar phase and immobilize TFSI− anions by electrostatic interaction. As a result, the PVDF‐HFP electrolyte with Li‐MOF‐F (LMF‐PE) achieves the highest polarity and Li transference number. In Li/Li symmetric cell tests, LMF‐PE demonstrates stable Li plating/stripping behavior without dendrites. Additionally, we applied lithium nickel manganese cobalt oxide (NCM) with 94% Ni content as a cathode material for cell test. LMF‐PE cell delivers a high initial discharge capacity of 226.9 mAh g−1 and 80% capacity retention after 150 cycles, highlighting its superior cycling performance. These enhancements are attributed to the structural and electrostatic benefits of Li‐MOF‐F.