Magnesium (Mg) metal is a promising electrode material for batteries application considering its high volumetric capacity, low cost, safety and environmentally benignity. This translates into the fact that Mg-based batteries can be manufactured in small dimensions (without decreasing the capacity) with a lower cost over the current state-of-art lithium (Li-) based batteries. In the recent years, this is evidenced from a growing number of prototype, showing the capability of Mg-based battery in producing a large current density with a high reversible capacity. However, the reliability of Mg electrode is critical as Mg metal undergoes a rapid Mg dissolution reaction, causing a short lifetime of the electrode and battery. The details of Mg electrochemistry is very complex and unique compared to other alkali and alkali earth metals. For instance, during anodic polarisation Mg has a capability to support hydrogen evolution reaction at a high rate. An understanding of reaction mechanisms at the interface can provide significant information on obtaining a desirable electrochemical performance for Mg electrode, which is beneficial for the development of stable and consistent performance of Mg-based batteries.

In this study, we recently investigated the electrode/ electrolyte interactions of Mg-based electrodes in aqueous electrolytes using a first-principles approach combined with the electrochemical characterisations. The classical description of the Mg electrochemical reaction is complicated by the formation of passive layer, dissolution of Mg and evolution of hydrogen gas. These reactions occur simultaneously and are often associated with the decreasing Coulombic efficiency and parasitic discharge that could lead to the premature battery failure. By recognising the importance of each individual reaction at the interface, we can selectively control the reactions; thus, providing a practical approach to engineer the electrochemical performance of Mg electrode and battery. With this knowledge, it is expected that a viable approach to optimise the use of Mg electrode can be achieved in both primary and secondary batteries, regardless of the electrolyte.