Multifunctional Separator Enabling Dendrite‐Free and Long‐Cycle‐Life Sodium Metal Batteries in Carbonate‐Based Electrolytes

Abstract 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 Na 3 V 2 (PO 4 ) 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.