Magnesium batteries: Current picture and missing pieces of the puzzle

Rechargeable magnesium batteries are gaining a lot of interest due to promising electrochemical features, which, at least in theory, are comparable than those of Li-ion batteries. Such performance metrics can be achieved by using thin metal foils or high-capacity alloys coupled with suitable electrolytes enabling a high Coulombic efficiency and use of a high energy density cathode materials. All three components significantly influence electrochemical characteristics and energy density of rechargeable magnesium batteries. Although there are many reports showing progress in the cyclability and stability of different systems, only few cathode materials promise possible commercialization. Remaining issues with efficiency, magnesium anode processing and electrolyte compatibility with cell housing are preventing faster development of technology with high possible impact on the future battery landscape. In the given perspective paper a critical overview on electrolytes, anode materials and three different classes of cathode materials is reported. Different rechargeable magnesium battery configurations were assumed and their dependence of volumetric energy densities on gravimetric energy densities are provided assuming realistic conditions with optimized electrode thicknesses and loadings, electrode porosity and optimized electrolyte quantity. Although calculated values are attractive, further experimental steps are needed in order to prove these numbers on the lab-scale and small prototype cells.