Reductive Competition Effect-Derived Solid Electrolyte Interphase with Evenly Scattered Inorganics Enabling Ultrahigh Rate and Long-Life Span Sodium Metal Batteries

Constructing an inorganic-rich and robust solid electrolyte interphase (SEI) is one of the crucial approaches to improving the electrochemical performance of sodium metal batteries (SMBs). However, the low conductivity and distribution of common inorganics in SEI disturb Na + diffusion and induce nonuniform sodium deposition. Here, we construct a unique SEI with evenly scattered high-conductivity inorganics by introducing a self-sacrifice LiTFSI into the sodium salt-base carbonate electrolyte. The reductive competition effect between LiTFSI and FEC facilitates the formation of the SEI with evenly scattered inorganics. In which the high-conductive Li 3 N and inorganics provide fast ions transport domains and high-flux nucleation sites for Na +, thus conducive to rapid sodium deposition at a high rate. Therefore, the SEI derived from LiTFSI and FEC enables the Na∥Na 3 V 2 (PO 4 ) 3 cell to show 89.15% capacity retention (87.62 mA h g –1 ) at an ultrahigh rate of 60 C after 10,000 cycles, while the cell without LiTFSI delivers only 48.44% capacity retention even after 8000 cycles. Moreover, the Na∥Na 3 V 2 (PO 4 ) 3 pouch cell with the special SEI presents a stable capacity retention of 92.05% at 10 C after 2000 cycles. This unique SEI design elucidates a new strategy to propel SMBs to operate under extreme high-rate conditions.