Sodiophilic Zn‐Diamane Ion Rectification Layer Modulated Polypropylene Separators Enable Dendrite‐Free Sodium Metal Batteries

Abstract Sodium (Na) metal is regarded as an ideal anode for sodium metal batteries (SMBs) due to its high theoretical specific capacity and low electrochemical potential. However, its utilization is still restricted by the notorious dendrites and unstable solid electrolyte interface (SEI). Herein, a zinc nanoparticle decorated 2D diamond (diamane) modulated commercial polypropylene (Zn‐diamane/PP) separator is dedicated to mitigating these issues for the longevity of sodium metal anodes. Interestingly, the sodiophilic Zn‐diamane/PP separator significantly accelerates the sodium ion mobilization and promotes a uniform flux, thus effectively preventing dendrite growth and enhancing the stability of the SEI layer. A Na||Na symmetric cell with Zn‐diamane/PP separator demonstrates a prolonged lifespan exceeding 5000 h at 1 mA cm⁻² with 1 mAh cm⁻². Notably, it sustains stability for >1000 h at an ultra‐high current density at 25 mA cm⁻² with 1 mAh cm⁻². The dendrite‐free deposition morphology and the formation of an inorganic‐rich inner SEI layer have been investigated through comprehensive characterizations and theoretical calculations analysis. Furthermore, a full cell comprising a Na₃V₂(PO₄)₃@C cathode, Zn‐diamane/PP separator, and Na metal anode demonstrate a high reversible capacity of 90 mAh g⁻¹ over 500 cycles. These results demonstrate the potential of Zn‐diamane/PP separator for long‐cycle lifespan SMBs.