Multifunctional Separator Enabling Dendrite-Free and Long-Cycle-Life Sodium Metal Batteries in Carbonate-Based...

Sodium metal batteries (SMBs), leveraging the natural abundance of sodium and high theoretical capacity, emerge as promising candidates for next-generation energy storage. However, the generation of the unstable solid electrolyte interphase (SEI) layer and uncontrolled Na dendrite growth in SMBs with carbonate-based electrolytes leads to poor Coulombic efficiency and security risks. Herein, a multifunctional separator (N-U@PE) for SMBs is fabricated through an innovative strategy involving the in situ growth of zirconium-based metal-organic frameworks (Zr-MOFs) on NASICON-type fast-ion conductor to prepare a dual-phase composite (N-U) as PE separator modification. Benefiting from abundant open metal sites (OMSs) and 3D ion transport channels, the N-U@PE separator can effectively immobilize anions and induce the formation of NaF-rich SEI layer, resulting in Na⁺ flux homogenization and Na⁺ transport kinetics enhancement. Satisfactorily, the Na|N-U@PE|Na symmetric cell achieves stable cycling for 3000 h at 0.5 mA cm^-2 and 0.5 mAh cm^-2. Remarkably, the Na₃V₂(PO₄)₃|N-U@PE|Na pouch cell exhibits 95.2% capacity retention after 1000 cycles at 2 C. The design of N-U@PE integrates ion transport regulation and interfacial stability, giving a practical solution for high-performance SMBs.