Tailoring a High Loading Atomic Zinc with Weak Binding to Sodium Toward High-Energy Sodium Metal Batteries

Single-atom materials provide a platform to precisely regulate the electrochemical redox behavior of electrode materials with atomic level. Here, a multifield-regulated sintering route is reported to rapidly prepare single-atom zinc with a very high loading mass of 24.7 wt.% by significantly improved diffusion kinetics and stronger charge transfer between zinc and nitrogen atoms. X-ray absorption near edge structure (XANES) spectra for Zn K-edges during the charge and discharge process verify the stable single-atom zinc structure and the reversible slight reduction and oxidation of Zn sites, which is much different from the previous report of the alloying reaction process. This result suggests atomic Zn acts as an active sites through weak binding with sodium to regulate the Na ion fluxes. Finally, Cu foil coated with a ≈2 µm layer of such material exhibits a high Coulombic efficiency of ≈99.99% up to 1700 cycles at 1 mA h cm^-2. An ultra-low overpotential of 3 mV and an unprecedented life span of over 3200 h in a symmetrical cell is achieved. Due to the very thin coating layer, anode-free sodium battery fabricated by Na₃V₂(PO₄)₃ cathode displays a prominent energy density of 320 Wh Kg^-1, demonstrating strong potential in practical application.