Embedding a percolated dual-conductive skeleton with high sodiophilicity toward stable sodium metal anodes

Abstract

The high theoretical capacity and earth-abundancy of metallic sodium (Na) endow it with high potential as the ultimate anode for batteries based on Na-ion chemistry. Nevertheless, dendritic Na, the unstable solid electrolyte interphase (SEI) and an infinite volume change of Na metal, drive rapid cell deterioration and potential safety hazards. In tackling these challenges, we take advantage of the spontaneous reaction between molten Na and SnO2 that triggers the formation of a percolated Na–Sn alloy/Na2O framework throughout Na metal, effectively anchoring the “hostless” Na into a dual ion/electron-conductive matrix and simultaneously improving the electrode surface chemistry. By density functional theory (DFT) calculations, we validate the high “sodiophilicity” and low Na+ diffusion barrier enabled by the Na–Sn alloy/Na2O framework. As such, stable Na plating/striping is realized in symmetric cells using both carbonate and ether-based electrolytes without any additive. The full cell paired with Na3V2(PO4)3 cathode further demonstrates superior capacity retention of 83% over 300 cycles (1C), along with a promising rate performance at 10C.