Calcium zincate as an efficient reversible negative electrode material for rechargeable zinc-air batteries

摘要

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)(4)(2-)) during discharging; most of it converted to calcium zincate. Cyclic testing established a second discharge capacity of 284mAhg(-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.