An in-situ formed stable interface layer for high-performance sodium metal anode in a non-flammable electrolyte

Sodium metal batteries (SMBs) have huge potential for applications in large-scale energy storage systems because of their high energy density, low cost and abundant resources. However, SMBs suffer from challenging problems, such as low reversibility and dendrite growth during plating/stripping. In this work, we report that a non-flammable electrolyte with Fluoroethylene carbonate (FEC) and 1,3,2-Dioxathiolane 2,2-dioxide (DTD) can in-situ generate a stable solid-electrolyte-interface (SEI) layer, which effectively suppresses the side reactions and prevents dendrite growth. This is attributed to the synergy of the multi-component of SEI layer including S-containing compounds (Na2S, Na2SO3 and organic S-containing salts), NaF and phosphate (Na3PO4). The DTD additive significantly promotes the stability and integrity of the formed SEI layer, which not only enables the dendrite-free Na plating/stripping with an average CE as high as 93.4% for 250 cycles, but also makes the Na parallel to Na symmetric cell stable over more than 1350 h at 1 mAh cm(-2) and 720 h even at 5 mAh cm(-2) .

Automated summary

By using a non-flammable electrolyte, a stable solid-electrolyte-interface (SEI) layer was successfully generated in situ, effectively suppressing side reactions and dendrite growth in sodium metal batteries. The addition of DTD promoted the stability of the SEI layer, allowing for dendrite-free sodium plating/stripping with high coulombic efficiency and long-term stability in Na symmetric cells.