Capacity‐Limited Na–M foil Anode: toward Practical Applications of Na Metal Anode

The practical applications of Na metal anodes are severely plagued by unstable Na plating/stripping. Here the fabrication of Na-rich Na-M (M = Au, Sn, and In) alloy anodes is reported as promising alternatives to address this issue. As compared to metallic Na foil anodes, the alloy foils exhibit improved electrolyte/electrode interface and provide abundant sodiophilic sites for efficient Na plating, while the self-evolved porous Na-M structures accommodate volume variation on cycling. Among three alloy foils, the Na-Au system shows the most promising performance. Under practical conditions such as capacity-limited anodes (5 mAh cm-2 ) and large stripping/plating capacity (1.0 mAh cm-2 ), the Na0.9 Au0.1 anodes demonstrate stable plating/stripping over 350 h. The proof-of-concept full cells assembled with hard carbon or Prussian blue materials and this thin Na0.9 Au0.1 anode also have much elongated cycling life than for pristine Na metal anodes. These findings confirm that the rational design of Na-M alloy anodes can be a promising strategy to promote the development of Na metal batteries.