Multifunctional Artificial Surface Layer to Realize Stable Na Metal Anode in Ether and Carbonate Electrolyte

Abstract

Sodium (Na) metal anode is the essential component of low-cost and high-performance Na metal batteries, yet its application is hampered by the unstable anode/electrolyte interface and inevitable growth of Na dendrites. In this work, a hierarchically porous artificial surface layer with sodiophilic silver (Ag) nanoparticles decorating the bottom surface (HPFA) is reported, which can regulate the uniform deposition of Na and eliminate the local overgrowth of dendrites on the surface of Na substrate. The dependence of Na deposition behavior on the hierarchical structure of surface layers is revealed by operando optical microscopy and multiphysics simulation, indicating the multifunction of the HPFA layer in stabilizing the Na anode during the electrochemical plating/stripping process. The as-fabricated HPFA/Na anode depicts prolonged life-span and improved stability in both ether and carbonate electrolytes, while the symmetric cell shows no sign of short-circuit even after 1200 h of repeated charging/discharging at 2 mA cm⁻² with a high area capacity of 4 mAh cm⁻². Besides, when the HPFA/Na anode is paired with Na₃V₂(PO₄)₃ cathode and ether electrolyte, the full cell exhibits a low decay rate of ≈0.28% with a stable coulombic Efficiency value of ≈99.88% at 2 C rate.