Effect of plant extract additives on the parasitic reaction in alkaline Zn-air batteries

Abstract

The battery's high energy density, economical price, and ecological sustainability of the Zn-air battery make it a bright future battery technology. However, parasitic reactions, which can diminish the battery's life cycle and efficacy, are the key challenges for potential development of Zn-air batteries. Glycyrrhiza glabra roots extract (GGRE) has been investigated as an alternative hydrogen gas evolution and corrosion inhibitor for Zn-air batteries in order to mitigate the parasitic reaction. The results obtained reveal that the inhibition capacity of the GGRE extract increases with concentration and reaches its highest level (75.6 %) around 350 mg l^-1 of GGRE extract. GGRE extract is a mixed type inhibitor with a predominately cathodic effect based on the polarization data. The GGRE extract adsorption on the Zn surface complies with Freundlich isotherm. In comparison to the blank Zn-KOH (354 mAh g^-1), the battery containing 350 mg l^-1 GGRE extract has the highest discharge capacity (533 mAh g^-1) and the best cyclability (92.9 % retention after 500 cycles). Overall, GGRE extract can significantly optimize the performance of Zn-air batteries.