Abstract
Zinc-air flow batteries exhibit high energy density and offer several appealing advantages. However, their low efficiency of zinc utilization resulted from passivation and corrosion of the zinc anodes has limited their broad application. In this work, ethanol, which is considered as an environmentally friendly solvent, is examined as an electrolyte additive to potassium hydroxide (KOH) aqueous electrolyte to improve electrochemical performance of the batteries. Besides, the effects of adding different percentages of ethanol (0–50% v/v) to 8 M KOH aqueous electrolyte were investigated and discussed. Cyclic voltammograms revealed that the presence of 5–10% v/v ethanol is attributed to the enhancement of zinc dissolution and the hindrance of zinc anode passivation. Also, potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that adding 5–10% v/v ethanol could effectively suppress the formation of passivating layers on the active surface of the zinc anodes. Though the addition of ethanol increased solution resistance and hence slightly decreased the discharge potential of the batteries, a significant enhancement of discharge capacity and energy density could be sought. Also, galvanostatic discharge results indicated that the battery using 10% v/v ethanol electrolyte exhibited the highest electrochemical performance with 30% increase in discharge capacity and 16% increase in specific energy over that of KOH electrolyte without ethanol.
Highlights
Zinc-air batteries are attractive for various future energy applications due to their low cost, high safety, high specific energy density, and environment-friendliness[1,2,3]
This work aims at enhancing electrochemical performances of zinc-air flow batteries by introducing ethanol in 8 M KOH aqueous electrolyte to suppress corrosion and passivation effects of granular zinc anodes
The oxidation of zinc, known as zinc dissolution, is the primary reaction determining the electrochemical performance of the zinc anode
Summary
Zinc-air batteries are attractive for various future energy applications due to their low cost, high safety, high specific energy density, and environment-friendliness[1,2,3]. Enormous research effort has been carried out to enhance the battery performance by improving the electrolyte as this approach is simple and does not affect the specific energy of the battery[6,7,8]. Alkaline aqueous electrolytes such as potassium hydroxide (KOH)[9], sodium hydroxide (NaOH)[10] and lithium hydroxide (LiOH)[11] are widely implemented in various types of batteries[3]. Non-aqueous electrolytes such as ionic liquids have been studied[18,19] Their high cost and sluggish reaction kinetic of oxygen reduction reaction cathode hinder their practical use[20]
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