The Key Role of Magnesium Polysulfides in the Development of Mg-S Batteries

The magnesium–sulfur (Mg-S) battery has been investigated in the past decade due to its high theoretical capacity and low active material cost. However, there are still several key issues that have not been overcome to enable practical Mg-S batteries. In this Perspective, the reasons for the poor performance of the Mg-S battery compared to its Li counterpart are discussed. The unique properties of magnesium polysulfides and the resulting passivation problem of the Mg anode are emphasized in this Perspective to facilitate progress in Mg-S battery research.