A system for recharging Zn-air battery with high reversibility using a water-in-salt electrolyte

Despite being a subject of interest for a very long time, rechargeable Zn-air batteries suffer from some funda-mental limitations, one of them being plating of zinc. With the introduction of water-in-salt electrolytes, it has become possible to achieve a fairly reversible zinc anode vis-a-vis plating and stripping. In the present work, we propose a twin chamber rechargeable Zn-air battery which utilizes exclusively a water-in-salt electrolyte for the zinc plating reaction, while the oxygen evolution reaction takes place in traditional dilute electrolyte. A third redox couple in the form of two auxiliary electrodes is used to decouple the zinc plating and oxygen evolution reaction. The auxiliary electrodes change their states after charging of each chamber which enables charging of the other chamber after switching of electrolyte positions. The active material for the auxiliary electrodes is chosen to be Na2V6O16 nanofibers. Meanwhile, the discharging can be performed with a dilute electrolyte, similar to a traditional Zn-air battery. The present work aims to demonstrate the operation of the proposed Zn-air battery system and present some insights on electrochemical behavior of Na2V6O16 in both ZnCl2 water-in-salt electrolyte and a ZnSO4 based dilute electrolyte.