Metal-organic framework-supported polymer oriented nanofibers separator for high-performance sodium metal batteries

Sodium metal is considered a potential candidate for the anode in next-generation cost-effective and high-energy-density metal batteries. However, its practical application in ether-based electrolytes is severely hindered by the uncontrolled proliferation of sodium dendrites and the instability of the solid electrolyte interphase (SEI) layer. To address these challenges, we developed a lightweight, multifunctional separator using electrospinning technology. This separator, composed of a polymer-metal-organic framework composite (PAN/ZIF-67), offers a novel alternative to conventional bulky glass fiber separators. The PAN/ZIF-67 separator features a unique ordered structure and open active metal sites, which significantly enhance electrolyte wettability and promote anion adsorption, effectively guiding the uniform deposition of Na + . Experimental results confirmed its superior electrochemical performance, including low polarization voltage and high cycling stability, under standard ether-based electrolyte conditions without additives. In symmetric Na || Na cells equipped with the PAN/ZIF-67 separator, exceptional cycling stability was achieved, with a low polarization voltage of ∼12 mV at 1 mA cm −2 sustained over 1000 h and ∼66 mV at 5 mA cm −2 for over 500 h. In a full cell with a Na₃V₂(PO₄)₃ cathode and Na anode, the separator demonstrated excellent rate capability and cycling stability, maintaining a capacity retention of 72.4 % after 800 cycles at 5C. This work offers a possible solution to address critical issues in sodium metal batteries and represents a notable advancement toward their practical applications.