Stable cycling of Na metal anodes in a carbonate electrolyte.

It is significantly challenging to stabilize sodium metal anodes in carbonate electrolytes. Here, we report that a sodium metal anode can achieve a high coulombic efficiency of up to ∼97% over 400 cycles at 0.1 mA cm-2 in a carbonate electrolyte with NaAsF6 as an additive. It is revealed that the SEI layer contains a large amount of NaF and O-As-O polymer which enables the stable cycling of sodium metal anodes.