A Multifunctional Na₂Se/Zn-Mn Skeleton Enables Processable and Highly Reversible Sodium Metal Anode

The recent high-energy density sodium (Na) metal batteries (SMBs) are restricted by their processability, lifetime, and safety. These issues can be addressed by controlling the reactions at the Na metal by modifying the Na metal anode (SMA) with the sodiophilic hosts. Herein, a multifunctional Na₂Se/Zn-Mn skeleton is introduced for SMA and fabricate a processable Na@Na₂Se/Zn-Mn composite using repeated cold rolling/folding approach through the spontaneous reaction between Na metal and ZnMnSe alloy. This unique intermetallic composite has Zn and Mn metal sites for uniform deposition of Na, while Na₂Se generates a stable SEI for rapid Na⁺ ion transport. It offers outstanding sodiophilicity, high processability, excellent mechanical strength, and high ionic conductivity due to the synergistic effect of multi-component, enabling stable Na plating/stripping at high current densities and areal capacities. An optimized Na₂Se/Zn-Mn skeleton enables Na||Na symmetric cells to attain a high critical current density of 5.0 mA cm^-2 at 5.0 mAh cm^-2 with an extended lifespan of 9000 h at 1.0 mA cm^-2 at 1.0 mAh cm^-2. Remarkably, when configured into a full cell with a Na₃V₂(PO₄)₃ cathode, the SMB displays an extended lifespan of 2000 cycles at 10 C and an impressive high-rate capacity of ≈61.6 mAh g^-¹ at 30 C.