Debating the magnesium–selenium battery technology

Magnesium ion batteries (MIBs) have received tremendous research attention owing to their low cost, dendrite free electroplating, and high theoretical capacities compared with lithium ion batteries (LIBs). Despite these advantages, the launching of MIBs is hindered by sluggish kinetics of the magnesium ions inside the host cathodes. Recently, several magnesium–selenium batteries have been developed to achieve the fast kinetics of magnesium ions inside the selenium-based cathodes. Herein, we have critically reviewed the five-year advancements made in the field of selenium cathode design, selenium loadings, compatible organic and inorganic electrolytes, their resultant reversible capacities, working voltages, cycle life, and specific energies. Selected selenium-based cathodes were critically debated in terms of their electrochemical performance and challenges. At the end of this review article, several innovative directions are proposed to shed light on future research.