High-rate sodium metal batteries enabled by trifluormethylfullerene additive

Sodium metal is a promising anode for sodium batteries due to its high theoretical capacity and low cost. However, the serious Na dendrite growth and low Coulombic efficiency, especially at high current densities/cycling capacities, severely limit the application of sodium metal anodes. Herein, trifluoromethylfullerene, C-60(CF3)(6), is designed as an electrolyte additive to enable the high-rate cycling of sodium metal anodes with high Coulombic efficiency. The CF3 groups contribute to the formation of stable NaF-rich solid electrolyte interface layer, while C-60 cages induce the uniform distribution of sodium ions and promote the formation of smooth and compact morphology. Thus, Na||Cu cell with C-60(CF3)(6) can be cycled at 2 mA center dot cm(-2) and 10 mAh center dot cm(-2) over 180 cycles with an average Coulombic efficiency of 99.9%, and Na parallel to Na cell can be cycled at 10 mA center dot cm(-2) over 600 cycles. Furthermore, Na parallel to NaV2(PO4)(3)@C full cell exhibits high capacity retention of 84% over 2,000 cycles at 20 C (similar to 3 mA center dot cm(-2)).

Automated summary

By adding trifluoromethylfullerene as an electrolyte additive, the Coulombic efficiency and cycling rate of sodium metal anodes can be improved, enhancing the performance of sodium batteries.