Synergistic Enhancement of Ion Flux Homogenization and Anion Anchoring in ZIF-67/Glass Fiber Composite Separators for Sodium Metal Batteries

Sodium metal batteries have emerged as a significant alternative to lithium-ion batteries due to their superior energy density, low cost, and abundant resource availability. However, sodium dendrite issues remain one of the primary bottlenecks limiting the broader adoption of sodium metal batteries. Modifying the separator material to induce uniform Na⁺-ion deposition is a key strategy for suppressing sodium dendrite growth in sodium metal batteries. Herein, a composite separator has been designed by coating one side of a glass fiber separator with a layer of ZIF-67 material modified with a small amount of cetyltrimethylammonium bromide. Owing to the synergistic effect of ZIF's inherent abundant microporous structure homogenizing the ion flux and cetyltrimethylammonium bromide anchoring ClO₄⁻, the glass fiber/ZIF-67-2 composite separator exhibits outstanding electrochemical performances: The Na||Na symmetric battery operated stably for 170 h at a current density of 1 mA cm⁻², while the Na||Na₃V₂(PO₄)₃ (NVP) asymmetric battery exhibited a remaining capacity of 54.4 mAh g⁻¹ after 1000 cycles at 10 C.