No abstract

Zn alloy electrodes containing 10 wt. % Al were prepared to examine the applicability as anodes in primary Zn–air batteries with neutral 2M NaCl electrolyte. These electrodes were investigated by electrochemical measurements and microscopic techniques (SEM, LSM, AFM). Based on the cyclic voltammetry and intermediate term (24 h) discharge experiments, the only active element in the as-prepared alloy was found to be Zn. It was further confirmed by LSM that Zn rich areas dissolved while Al remained passive during discharge. The passive state of Al was also demonstrated by conductive AFM investigations on the as-cast alloy surfaces. The results on potentiodynamic polarization and weight loss measurements indicated that the alloy electrode was less prone to corrosion than pure Zn electrode. The electrochemical behavior of the electrodes was modified under certain cathodic polarization previous to measurements. Accordingly, originating from Al activation due to application of cathodic potentials, potentiodynamic polarization studies showed a clear shift on the corrosion potentials of the alloy toward more negative values. On the basis of these results, with the precondition of Al activation prior to discharge experiments, the effect of Al alloying on the Zn electrodes was revealed as temporarily enhanced potentials on the discharge profiles in comparison to pure Zn electrodes.

The influence of ethylenediaminetetraacetic acid (EDTA) electrolyte additive on the performance of ZnÀ air batteries with nearneutral 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 À 2 around À 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 À 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 ZnÀ air cells with EDTA were operated up to 930 h with specific energies up to 840 Wh kg Zn À 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 ZnÀ air cells showed better performance in terms of higher discharge voltage, discharge energies, and lower overpotentials in presence of EDTA.

The Cover Feature illustrates how the EDTA “spell” prevents the hydra from corrupting the “place of power”, which otherwise would not be able to efficiently power the city. Hydra′s heads are representing H2O and Cl−, which result in formation of quasi‐passive films by blocking the purple Zn2+ ions at the surface. The presence of EDTA, on the other hand, prevents the formation of such passivating films due to its remarkable Zn2+‐chelation ability and directly leads to improved electrochemical performance of the Zn electrodes in resource‐efficient Zn‐air batteries. More information can be found in the Article by Y. E. Durmus and co‐workers.