Mg batteries are an attractive next-generation energy storage option due to the high volumetric capacity of the Mg-metal anode compared to traditional Li-intercalation anodes such as graphite. Pairing the Mg anode with a S8 cathode produces an economical cell from sustainable materials, however, designing electrolytes compatible with both Mg and S8 is challenging. I will discuss my work determining the effect of solvent on S8 reduction in Mg-S batteries and passivation at the Mg anode. Preparing Mg electrolytes with varied solvent systems is difficult due to the strong dependence of Mg2+ speciation on the solvent. To study the effect of solvent, the magnesium aluminum chloride complex (MACC) electrolyte was prepared in various ethereal solvents. Reversible Mg electrodeposition and stripping was demonstrated in the MACC electrolyte and the electrodeposition overpotentials and current densities were found to vary with solvent. The S8 reduction chemistry was also found to be dependent on the electrolyte composition, suggesting solvent-mediated reduction pathways. The reduction products and reduction mechanisms are found to be different from the analogous Li-S system and begin to provide insight into the redox mechanisms of the Mg-S cell. Importantly, the reactivity of the Mg surface with the electrolytes is found to be of significant importance and methods to bypass this limitation will be presented.

S8 reduction processes and Mg reactivity in a Mg-S8 battery

2019 Fall National Meeting

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