Practical Limitations Associated with Metallic Magnesium Sulphur Batteries

Abstract

Rechargeable magnesium batteries (RMBs) have attracted a lot of attention in recent decades due to the theoretical properties of these systems in terms of energy density, safety, and price. Nevertheless, to date, fully rechargeable magnesium battery prototypes with sufficient longevity and reversibility were realized only with low voltage and low capacity intercalation cathodes. The community is therefore actively looking for high-capacity cathodes that can work with metallic magnesium anodes in viable RMB systems. One of the most promising cathode materials, in terms of very high theoretical specific capacity is sulfur. A number of recent works studied the electrochemical performances of rechargeable sulfur cathodes in RMB, with success to some extent on the cathode side. Nevertheless, the formation of soluble polysulfide’s during discharge affects strongly the behavior of the anode side. we are focusing on soluble polysulfide impact on Mg–S electrochemical systems. We carefully designed herein conditions that mimic the Mg–S battery prototypes containing balanced Mg and elemental sulfur electrodes. Under these conditions, we extensively studied the Mg anode behavior. The study shows that when elemental sulfur cathodes are discharged in the Mg–S cells containing electrolyte solutions in which Mg anodes behave reversibly, the polysulfide species thus formed migrate to the anode and eventually fully passivate it by the formation of very stable surface layers.