Nucleophilic Sn Seeding and Interface Engineering for Highly Stable Sodium Metal Batteries

Sodium metal is a promising anode material for energy storage beyond lithium-ion batteries due to its abundance and low cost. However, the uncontrolled growth of dendrites and associated safety concerns have limited the practical application of sodium metal batteries (SMBs). By embedding nucleophilic tin seeds in a free-standing carbon film (FSF), here, an effective solution is developed to stabilize the sodium metal anode. The highly conductive and porous carbon matrix, intimately embedded with abundant Sn seeds (C@Sn), enables remarkably uniform sodium plating, and provides long-term stability for SMBs. Mechanistic studies confirm the formation of an Na─Sn alloy on interface which helps to lower the nucleation barrier for sodium plating. Hence, symmetric sodium cells equipped with C@Sn FSFs can sustain uninterrupted sodium plating and stripping for almost 2600 h at a high areal capacity of 4 mA h cm^-2, achieving an average Coulombic efficiency (CE) of 99.88%. In addition, full cells prepared with commercial Na₃V₂(PO₄)₃ cathode and C@Sn-FSFs anode deliver remarkable cycling (90 mA h g^-1 beyond 1300 cycles at 1C) and excellent rate performance. This ingenious strategy of embedding Sn particles within a carbon matrix offers an overall compelling solution to enhance the longevity of sodium anodes.