Calcium Zincate As an Efficient Reversible Negative Electrode Material for Rechargeable Zinc–air Batteries

A zinc anode suffers from poor reversibility. Among the materials designed to improve the reversibility, calcium zincate has electrochemical properties that make it suitable as a negative electrode material for alkaline secondary batteries. Nevertheless, there are few precedents for using it in zinc–air secondary batteries. In this study, calcium zincate was synthesized using a chemical co-precipitation method and its physical properties were studied by X-ray diffraction and thermogravimetric analysis. The synthesized calcium zincate was used as the negative electrode of a rechargeable zinc–air battery. It was reduced to zinc metal during charging and oxidized to zincate ion (Zn(OH)42−) during discharging; most of it converted to calcium zincate. Cyclic testing established a second discharge capacity of 284 mAh g−1 and a coulombic efficiency of 96% for the whole cycle, which is unprecedented for zinc–air batteries. The “charging efficiency” was first proposed as a measure of the amount of side reactions that occur during cycling.