Mg Cathode Materials and Electrolytes for Rechargeable Mg Batteries: A Review

The development of energy storage devices has been motivated by the growing availability of sustainable energy sources, as well as the wider application of portable devices and a variety of electric vehicles including bicycles, scooters, cars and buses. Concerns regarding the safety of lithium batteries in certain applications, and limited lithium and cobalt resources required for conventional cathode materials, have driven researchers to develop alternatives that are safer and cheaper, thereby using more abundant metals such as sodium, magnesium, aluminium, and calcium. Among them, rechargeable magnesium batteries have drawn special interest, since Mg does not plate in a dendritic form, which opens up the possibility of the safe use of a simple metal anode. In this review, we summarize typical Mg electrolyte systems that are compatible with reversible Mg deposition and stripping, focusing on the active Mg complexes. To fabricate a rechargeable device, an appropriate cathode is necessary, which must also be abundant and compatible with the electrolytes to suitable cathode materials are also briefly discussed.