Stabilizing dendrite-free lithium metal batteries via an anionphilic ZIF-67 modified separator

Lithium metal batteries (LMBs) have garnered increasing attentions owing to their high theoretical capacity, but the issue of lithium dendrites and associated safety concerns have seriously hampered the real-world applications. Herein, using a well-designed ZIF-67 anionphilic metal-organic framework (MOF) as a Li⁺ solvent dissociator, a multifunctional separator regulating ion transport is successfully fabricated for stabilizing lithium metal electrodes. The continuous and homogeneous MOF separators are prepared by coating the uniform mixtures of ZIF-67 and the poly(vinylidene difluoride) (PVDF) on polypropylene (PP) separators. Notably, the well-developed unsaturated metal sites within the MOF can serve as anionphilic regulators for Li⁺-solvates, favorable for limiting the free migration behavior of anions. Besides, the inherent ionic nanochannels formed by large sodalite cages (11.6 Å) and small pore windows (3.4 Å) in the MOFs assist in enabling rapid transfer of Li⁺ (0.76 Å). It is found that the MOF separator effectively inhibits lithium dendrites and parasitic reactions. The Li|Li symmetric cell with the PP@ZIF-67 separator achieves uniform lithium deposition more than 700 h and steady cyclability even at 60 °C. In addition, the LiMn_0.7Fe_0.3PO₄|Li assembled with this multifunctional separator (PP@ZIF-67) demonstrates promoted rate capability and cycling stability. Constructing MOF-modified separators has emerged as a promising approach to enhance battery performance, facilitating in-depth research on the overall application of MOF in lithium batteries.