Dead Sodium Suppression Enabled by Sodiophilic Alloy-Seeded Carbon Scaffolds for Stable Sodium Metal Batteries

Constructing self-supporting, sodiophilic scaffolds to suppress inactive "dead sodium" accumulation and subsequent dendrite growth is crucial for the advancement of rechargeable sodium metal batteries. However, uniformly incorporating sodiophilic species into conductive scaffolds while maintaining sufficient buffer space to spatially regulate Na plating/stripping reversibility remains a formidable challenge. Herein, we report a three-dimensional multifunctional host featuring cucurbit-shaped nitrogen-doped carbon nanofibers uniformly embedded within pomegranate-like porous ZnNi alloys (Zn/Ni@NCF). Benefiting from its precisely engineered structure and composition, the Zn/Ni@NCF host enables an ultralow nucleation overpotential (as low as 8 mV), a high average Coulombic efficiency (>99.6% over 1100 cycles), and stable long-term cycling performance (>3200 h in symmetric cells), showing favorable electrochemical behavior compared with representative reported sodium metal anodes. Combined theoretical calculations and in situ/exsitu visualizations reveal that the outstanding performance originates from the high Na-binding energy of the alloy seeds, homogeneous Na-ion flux, and spatial confinement effect, which synergistically suppress dead sodium formation and dendrite growth. When this tailored host is integrated into anode-less full cells, the cells achieve 90.4% capacity retention after 200 cycles at 1C (surpassing control cells by more than 8-fold), while anode-free pouch cells exhibit impressive capacity and stability even under high current densities, indicating its potential for practical application. This work highlights the role of host-structure engineering in mitigating dead sodium and provides design principles for developing high-energy sodium metal batteries.