Synergistic Multi-Field Regulation via MOF–Polymer Hybrid Separators Enabling Dendrite-Free and Thermally Stable Lithium Metal Batteries

Lithium metal batteries (LMBs) offer exceptional energy storage potential but suffer from dendrite growth, SEI instability, and thermal risks. To address these challenges, a multifunctional composite separator (GF@UiO-66-NH₂ + HFP) combining a glass fiber with a metal-organic framework (MOF) layer and polymer coating is constructed to synergistically regulate ion transport, thermal behavior, and interfacial chemistry. The MOF selectively adsorbs PF₆^- anions and solvent species, disrupting Li⁺ solvation to generate weakly solvated ions for uniform deposition, while poly(vinylidene difluoride)-HFP aligns polymer chains to homogenize Li⁺ flux, overcoming inherent limitations of porous substrates. This dual-ion sieving/flux-homogenization strategy leads to a high Li⁺ transference number (0.96) and homogeneously regulates the ion concentration and electric and thermal fields, suppressing lithium dendrites growth while forming a robust inorganic-rich SEI dominated by Li₂O (inner layer) and LiF (outer layer). Consequently, the NCM811||Li cells achieve 89.3% capacity retention and 99.9% Coulombic efficiency after 200 cycles at 1 C. Notably, the functionalized separator enables >110 failure-free cycles at 80 °C, significantly outperforming conventional PP separators, primarily owing to its superior thermal regulation, which ensures structural integrity even at extreme temperatures (150 °C). This work proposes a paradigm-shifting approach for stabilizing LMBs through integrated multiphysics regulation, offering effective solutions for high-safety batteries with enhanced temperature adaptability and mechanical reliability.