Enhancing the Cycle Life of a Zinc–Air Battery by Means of Electrolyte Additives and Zinc Surface Protection

Abstract

The commercialization of rechargeable alkaline zinc–air batteries (ZAB) requires advanced approaches to improve secondary zinc anode performance, which is hindered by the high corrosion and dissolution rate of zinc in this medium. Modified (with additives) alkaline electrolyte has been one of the most investigated options to reduce the high solubility of zinc. However, this strategy alone has not been fully successful in enhancing the cycle life of the battery. The combination of mitigation strategies into one joint approach, by using additives (ZnO, KF, K2CO3) in the base alkaline electrolyte and simultaneously preparing zinc electrodes that are based on ionomer (Nafion®)-coated zinc particles, was implemented and evaluated. The joint use of electrolyte additives and ionomer coating was intended to regulate the exposition of Zn, deal with zincate solubility, minimize the shape change and dendrite formation, as well as reduce the hydrogen evolution rate. This strategy provided a beneficial joint protective efficiency of 87% thanks to decreasing the corrosion rate from 10.4 (blank) to 1.3 mgZn cm−1·s−1 for coated Zn in the modified electrolyte. Although the rate capability and capacity are limited, the ionomer-coated Zn particles extended the ZAB cycle life by about 50%, providing battery roundtrip efficiency above 55% after 270 h operation.

Keywords

• zinc–air
• electrolyte-additives
• electrodes-additive
• zinc electrode
• Nafion®
• ionomer coating