Highly reversible oxygen to superoxide redox reaction in a sodium-containing ionic liquid

- Oxygen reduction mechanisms in Na+/pyrrolidinium ionic liquid mixtures reported.
- Onset of the oxygen reduction shifts more positive on increasing Na+ concentration.
- Remarkable cyclic coulombic efficiency (74%) observed in Na+/pyrrolidinium mixture.
- These observations provide a research platform for new Na-air battery electrolytes.

Comprehensive studies regarding the impact of the electrolyte composition on the oxygen reduction mechanism are important to deliver highly efficient rechargeable sodium-air batteries. Thus, we report, for the first time, the oxygen reduction mechanisms and discharge products in a pyrrolidinium-based ionic liquid in the presence of different Na+ ion concentrations. Upon increasing the Na+ salt concentration, oxygen reduction becomes more efficient (e.g. 74%) and the onset potential of the reduction process shifts to a more positive value due to superior solvation of the superoxide anion by Na+. These observations should provide a platform of potential electrolytes for Na-air batteries.

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