Nitrogen-Rich Solvation Structures Enable Long-Cycle Sodium Metal Batteries

Sodium (Na) metal anode exhibits excellent prospects in rechargeable battery systems owing to its high theoretical capacity (1166 mAh g⁻¹) and its high abundance in the crust (2.3%). However, the electrochemical/mechanical unstable electrode interphases induce the rapid battery performance degradation and severely hinder the wide applications of Na metal batteries (SMBs). Herein, a nitrogen-enriched coordinated solvation structure (NECS) is designed to simultaneously stabilize both electrodes through the innovation of solvation-structure-derived interphases engineering. The NECS-derived N/O-rich inorganic solid electrolyte interphase enables uniform and dendrite-free Na plating/stripping for a working Na anode. NECS-derived cathode electrolyte interphase, composed of NaN_xO_y, Na₃N, and other Na containing compounds, significantly enhances the structural stability and electrochemical reversibility of the NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) cathode. The Na||Na symmetric cell with NECS electrolyte remains stable for more than 4000 h. Besides, the Na||NFM full cell achieves 1000 cycles with 86.1% capacity retention using a high loading electrode of 7.5 mg cm⁻². The Na||NFM pouch cell configuration demonstrates a high energy density of 202.6 Wh kg⁻¹, underscoring the practicality of the proposed electrolyte strategy. The strategy solvation structure modulation proposed in this work offers a universal approach to overcoming the challenge between high-energy-density and long-lifespan of SMBs.