Defect-functionality synergistic strategy enabling uniform Na plating for dendrite-free sodium metal anodes

Abstract

Sodium metal batteries (SMBs) are promising candidates for next-generation high-energy batteries due to the abundance and low cost of sodium. However, their practical deployment is hindered by uneven sodium deposition and dendritic growth, which leads to poor cycling stability and safety concerns. Herein, sodiophilic porous carbon hosts are fabricated via a defect engineering and surface functionalization strategy. The incorporation of moderate structural defects effectively reduces the sodium nucleation overpotential, while the oxygen-containing functional groups such as carboxyl (–COOH) and carbonyl (C=O) guides the formation of dense and uniform sodium layers. Theoretical calculations and experimental characterizations collectively reveal the synergistic role of defect sites and surface functionalities in promoting Na⁺ diffusion and regulating nucleation behavior. Consequently, the optimized ABC-11 achieves exceptional cycling stability with a Coulombic efficiency of 99.91 % over 1200 cycles at 1 mA cm⁻²/1 mAh cm⁻² in asymmetric cells. The Na@ABC-11 symmetric cell also exhibits ultra-stable plating/stripping durability exceeding 2200 h. Furthermore, the assembled Na₃V₂(PO₄)₃ || Na@ABC-11 full cell delivers a high reversible capacity of 102 mAh g⁻¹ and maintains 94 % of its initial capacity after 1200 cycles. This work highlights a cost-effective and scalable strategy for the structural design of carbon-based hosts, offering a viable pathway toward high-performance SMBs.