The effect of water admixture on aprotic Mg-O2 battery performance

Abstract

Generally, aprotic Li-O2 batteries performance is significantly influenced by water impurity in electrolyte/gas via promotion of Li2O2 mesocrystallization. In the case of promising alkali-earth metals this issue remains unexplored. Here we have studied the role of water content in DMSO-based electrolyte in discharge process of Mg-O2 cells with metallic magnesium anode and carbon cathode. We found that water impurity in the electrolyte is not a key factor determining the discharge capacity for a Mg-O2 battery, at least in a single-compartment cell. Morphology of discharge product does not change upon addition 8000 ppm of water. Discharge products contain major amount of electrolyte byproducts and negligible concentration of magnesium peroxide. Under high water content (more than 8000 ppm) Mg(OH)2 is also formed as discharge product, but content of by-products still remains high.