Understanding Interphase Formation in Magnesium Batteries

Lithium-ion batteries are used everywhere with their success being influenced by the solid electrolyte interphase (SEI) that coats the lithium electrode. However, their drawbacks relate to their unsustainable practices and safety problems, especially considering the thermal runaway that causes multiple battery fires. A valid solution is replacing the negative electrode (anode) with a different metal that can be sustainably sourced. In this regard, magnesium represents the most valuable alternative to lithium. Magnesium is orders of magnitude more abundant, safer, and has a higher volumetric capacity than lithium. However, the interphase coating the magnesium anode is ionically insulating compared with that at the lithium anode, holding magnesium batteries from future commercialisation. Despite being a promising technology, one of the major issues is to protect the magnesium electrode from parasitic side reactions without reducing its electrochemical activity, giving a requirement to generate an artificial SEI that is both ionically conductive and electronically insulating. Examples of these interphases from the literature include magnesium halide surface coatings.