(Digital Presentation) Effect of Electrolyte Additives on the Discharge Behavior and Performance of a WE43 Mg Alloy As Mg-Air Battery Anode

Abstract

Smartphones and electric cars have developed rapidly over the past ten years. Hence, high energy density storage devices are also getting increasing attention. Compared with commercial Li-ion batteries, Mg-air battery systems have the advantages of a high theoretical energy density (6800Wh/kg), natural abundance, environmental-friendliness, and low cost. However, Mg-air battery suffers from low anodic efficiency, discharge product accumulation, and sluggish reaction kinetics on both the anodes and cathodes. Adding additives to the electrolyte has been shown to increase the cell voltage and boost the anode efficiency. Nevertheless, the underlying mechanism of how electrolyte additives change the discharge behavior is still unclear. In this report, the discharge behavior and performance of a Mg-air battery with different electrolyte additives are investigated through a combination of electrochemical analysis, collection of the by-product hydrogen gas, and microscopic characterizations.A WE43 Mg alloy was selected as the anode for primary Mg-air batteries due to its high activity in 3.5wt% NaCl solution. Various amounts of electrolyte additives, such as chelating agents, e.g. salicylate salts, and corrosion inhibitors, e.g. Na3PO4, were added to 3.5wt% NaCl solution together or separately. The discharge behavior and performance with different additives were analyzed by recording the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) before and after discharge, discharge voltage evolution, hydrogen evolved from the anodes, and cross-sectional observations of the alloy after discharge. The anodic efficiency loss contributed by the negative difference effect (NDE) and chunk effect (CE) were also quantified to study how different additives change the discharge behavior. The anode performance improvement and synergic effect of the electrolyte additives will be discussed. Figure 1