Porous BN Nanofibers Enable Long-Cycling Life Sodium Metal Batteries

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 Na₃V₂O₂(PO₄)₂F/Ti₃C₂X 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.