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

Abstract

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.