Recent advances in electrolytes and cathode materials for magnesium and hybrid-ion batteries

The rechargeable magnesium ion batteries (MIBs) are ideal candidates to replace currently commercialized high energy density lithium ion batteries (LIBs) owing to their cost effective and environmentally friendly nature. However, bad performance of MIBs is a big challenge for researchers. In this review, we have critically discussed the state-of-the-art research activities made for the development of Mg-ion battery electrolytes and cathode materials with fast magnesiation kinetics. Emphasizing the chemical structures of both organic and inorganic electrolytes and their compatibilities with different cathode materials, the kinetic properties of electrochemical reactions for achieving optimized energy and power densities, are critically reviewed. To tackle the large polarizations of MIBs, the latest and emerging hybrid ion electrochemistries such as Mg-Li, Mg-Na, aqueous rechargeable Mg-Na, and Mg-Zn hybrid ion batteries, are highlighted to elaborate the merits and challenges of each electrolyte and nanostructured cathodes. The cathode materials covered in this review include various kinds of inorganic materials (i.e. metal oxides, metal sulfides), organic polymers, Prussian blue analogous and NASICON-type Li/Na cathodes with high working potentials. At the end, this review discuss comprehensive future research strategies for exploring new cathodes with high working voltages for MIBs.