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

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||NaNi1/3Fe1/3Mn1/3O2 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. A rooted multifunctional heterogeneous Solid Electrolyte Interphase layer is designed through a surface reconstruction approach for sodium metal anode (SMA). The prepared protective layer with synergistic effects, including large Young's modulus, high sodiophilicity, and rapid Na+ diffusion conduction can regulate the Na+ deposition behavior and strengthen the stability of the electrode, enabling dendrite‐free SMA and ultralong cycle lifespan of sodium metal batteries.