Porous BN Nanofibers Enable Long‐Cycling Life Sodium Metal Batteries

Abstract Sodium metal anode, featuring high capacity, low voltage and earth abundance, is desirable for building advanced sodium‐metal batteries. However, Na‐ion deposition typically leads to morphological instability and notorious chemical reactivity between sodium and common electrolytes still limit its practical application. In this study, a porous BN nanofibers modified sodium metal (BN/Na) electrode is introduced for enhancing Na‐ion deposition dynamics and stability. As a result, symmetrical BN/Na cells enable an impressive rate capability and markedly enhanced cycling durability over 600 h at 10 mA cm −2 . Density functional theory simulations demonstrate BN could effectively improve Na‐ion adsorption and diffusion kinetics simultaneously. Finite element simulation clearly reveals the intrinsic smoothing effect of BN upon multiple Na‐ion plating/stripping cycles. Coupled with a Na 3 V 2 O 2 (PO 4 ) 2 F/Ti 3 C 2 X cathode, sodium metal full cells offer an ultrastable capacity of 125/63 mA h g −1 (≈420/240 Wh kg −1 ) at 0.05/5 C rate over 500 cycles. These comprehensive analyses demonstrate the feasibility of BN/Na anode for the establishment of high‐energy‐density sodium‐metal full batteries.