Sodium metal is a promising anode for batteries because of its high theoretical specific capacity (1165 mAh g^-1) and great abundance and low cost. However, fundamental issues such as dendrite formation, “dead sodium” accumulation during cycling, fast SEI dissolution or continuous SEI growth bring challenges for stabilizing reversibility of sodium metal anode. Recent advances in electrolyte engineering and development of highly stable cathode materials have enables sodium metal batteries reaching high CE (>99 %) at room temperature^1-5.

Herein, we report a feasible pathway toward further stabilization of sodium metal anode using tetraglyme solvent (TEGDME) based electrolyte with various sodium salts (NaBF­_4, NaPF₆, NaTFSI, NaFSI, NaClO₄, NaOT_f). It is demonstrated that a Na||Cu cell exhibited an average Coulombic efficiency of 99.9 % over 200, 850, and 1000 plating-stripping cycles when an electrolyte of 1M NaOT_f in TEGDME, 1M NaPF₆ in TEGDME, and 1M NaBF₄ in TEGDME were used, respectively. Furthermore, 1M NaBF₄ in TEGDME electrolyte also enabled excellent cycling stability of Na||Na₃V₂(PO₄)₂ batteries at high rate (1 C) for 1000 cycles with capacity retention of 90.8 %.

References

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Acknowledgement

This work is supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy (DOE) through the Advanced Battery Materials Research (BMR) program under contract no. DE-AC05-76RLO1830.