Sodiophilic Ag-diamane-Modulated Polypropylene Separators for High-Performance Sodium Metal Anodes

Sodium metal is a promising anode material for sodium metal batteries (SMBs) due to its high theoretical specific capacity and low electrochemical potential. However, its practical implementation is severely limited by dendrite formation, which causes short circuits and safety issues. Here, we introduce a separator modification strategy using Ag nanoparticles decorated with two-dimensional diamane on a commercial polypropylene (PP) substrate (Ag-diamane/PP) to enhance the performance of sodium metal anodes (SMAs). The synergistic effect between the sodiophilic Ag nanoparticles and the diamane network not only accelerates Na⁺ transport through the modified separator but also reduces interfacial resistance. This dendrite-suppression effect was systematically validated using in situ optical microscopy and ex situ scanning electron microscopy. Symmetric Na||Na cells incorporating the Ag-diamane/PP separator exhibit exceptional cycling stability, maintaining more than 3800 h of operation at 2 mA cm^-2 with a capacity of 1 mAh cm^-2. Furthermore, a full-cell configuration with a Na₃V₂(PO₄)₃@C cathode, Ag-diamane/PP separator, and Na metal anode delivers a high reversible capacity of 94.35 mAh g^-1 and stable cycling for 270 cycles. This work highlights the Ag-diamane/PP separator as a promising solution for advancing dendrite-free SMBs with long-term cycling stability and high energy density.