A Rooted Multifunctional Heterogeneous Interphase Layer Enabled by Surface‐Reconstruction for Highly Durable Sodium Metal Anodes

Abstract Sodium plating–stripping with high reversibility is still an intractable challenge for sodium metal‐based batteries due to the fragile natural solid‐electrolyte interphase (SEI) film and severe Na dendrites growth. Herein, a surface reconstruction strategy is proposed and a rooted heterogeneous interlayer derived from in situ reactions between tin selenide and Na metal (abbr. Na/SnSe) is produced to regulate Na⁺ deposition behavior and impede dendrite growth. The high sodiophilic Na₁₅Sn₄ component demonstrates the robust combination and dendrite suppression capability, inhibiting fracture and delamination problems during volume variation. Meanwhile, the superionic Na₂Se ingredient contributes to the optimized Na⁺ conduction efficiency and low nucleation overpotential, enabling uniform distribution of electrical fields and ultimately eliminating Na dendrites. Consequently, the reconfigured multifunctional Na/SnSe interphase realizes a long‐term lifespan over 2400 h at 0.5 mA cm⁻²/1 mAh cm⁻² in symmetric cell with an extremely low voltage hysteresis. Moreover, the assembled Na/SnSe||NaNi_1/3Fe_1/3Mn_1/3O₂ pouch cell achieves exceptional cycling stability and capacity retention (90.4 mAh g⁻¹ after 1800 cycles at a high current density of 2 A g⁻¹), exploiting an avenue for designing durable SEI layer and high‐quality sodium metal batteries.