Improved Electrochemical Performance of Zinc Anodes by EDTA in Near‐Neutral Zinc−Air Batteries
Saúl Said Montiel Guerrero, Yasin Emre Durmus, Krzysztof Dzięcioł, Shibabrata Basak, Hermann Tempel, Stefan van Waasen, Hans Kungl, Rüdiger‐A. Eichel
Abstract
Abstract The influence of ethylenediaminetetraacetic acid (EDTA) electrolyte additive on the performance of Zn−air batteries with near‐neutral chloride‐based electrolytes was examined for primary and secondary batteries. The electrochemical measurements indicated that Zn is not completely active in neat 2 M NaCl, but still could be discharged up to 1 mA cm −2 around −1.0 V Ag/AgCl . The characterization of the Zn surfaces revealed the existence of a passive film consisting of Simonkolleite, Zn(OH) 2 , and/or ZnO. The EDTA additive enhanced the discharge voltages by 200 mV to −1.2 V Ag/AgCl indicating an active Zn surface. The effect of EDTA is explained by its chelation abilities with Zn 2+ before formation of hydroxide or oxide species. The Zn−air cells with EDTA were operated up to 930 h with specific energies up to 840 Wh kg Zn −1 . The cells could also be cycled up to 70 cycles while providing enhanced discharge voltages at 1.15 V over 50 cycles. The positive effect of EDTA is dependent on the amount of free EDTA molecules. Nevertheless, the Zn−air cells showed better performance in terms of higher discharge voltage, discharge energies, and lower overpotentials in presence of EDTA.