Dual-Functional Separator with High Li ⁺ Flux and Cation-Selective Transport for Dendrite-Free Lithium Metal Anodes

Lithium metal anodes (LMAs) hold great promise for enabling next-generation batteries with ultrahigh energy density, yet their practical use is hindered by dendrite growth and sluggish Li-ion transport, leading to safety concerns and poor rate capability. Here, we report a high Li-ion flux, cation-selective dual-functional separator (LCDS) fabricated by electrospinning poly(vinylidene fluoride-co-hexafluoropropylene) and polyacrylonitrile with uniformly dispersed ZIF-8 particles. The abundant lithiophilic C–F and C≡N groups in the fibrous matrix homogenize Li-ion flux, while ZIF-8 adsorbs PF6– anions, facilitating Li-ion predesolvation and modulating the interfacial solvation structure. These synergistic effects extend the induction time for dendrite formation, suppress side reactions, and enable uniform, dense Li deposition. In addition, the three-dimensional porous architecture provides rapid ion transport pathways and mechanical robustness, further stabilizing the Li metal interface. As a result, Li||Li symmetric cells with LCDS achieve stable cycling for 1800 h at 1 mAh cm–2 and 5 mA cm–2, while Li||LiFePO4 full cells retain 90% of their capacity after 350 cycles at 5 C. This work demonstrates an effective and scalable separator design strategy for enabling dendrite-free, high-rate Li metal batteries.