Separators are crucial in ensuring the safety and achieving high-energy densities of sodium (Na) metal batteries (SMBs). However, the cycling stability and safety of SMBs are compromised by commercial polymer separators and surface-modified separators due to their low melting point and poor ionic transport capabilities. In this study, we introduce an all-inorganic ceramic separator fabricated from boron nitride nanotubes. This design enhances ionic conductivity and the Na-ion transference number. The functionalized separator not only reduces the Na + diffusion barrier and facilitates uniform Na deposition but also diminishes the risk of explosion through heat dissipation. Consequently, the ceramic separator supports stable Na plating/stripping for over 956 h at 3 mA cm −2 and 840 h at 10 mA cm −2 . Furthermore, the Na//Na 3 V 2 (PO 4 ) 3 cell exhibits a markedly extended lifespan of 600 cycles with 94% capacity retention. This research opens new possibilities for designing all-inorganic materials for separators, aiming to achieve safe and stable sodium metal battery anodes.
Shen et al. (2026) studied this question.