Insights on solid electrolytes for solid-state magnesium batteries: progress and prospects

The development of new energy storage systems with high energy density is urgently needed due to the increasing demand for electric vehicles. Solid-state magnesium batteries are considered to be an economically viable alternative to advanced lithium-ion batteries due to the advantages of abundant distribution of magnesium resources and high volumetric energy density. As a critical component of solid-state magnesium batteries, solid magnesium-ion electrolytes offer advantages such as non-flammability, non-volatility, good thermal stability, and mechanical flexibility. Nevertheless, solid magnesium-ion electrolytes face crucial challenges, including low ionic conductivity and limited magnesium ion migration. Considerable research efforts have been carried out to explore suitable solid electrolytes and great progress has been made. Therefore, this review summarizes recent advances in solid magnesium-ion electrolytes, encompassing organic polymer, inorganic, and composite solid electrolytes. The composition, ionic conductivity, and magnesium ion transport mechanisms of these solid magnesium-ion electrolytes are discussed. Furthermore, this review highlights the strengths of various solid electrolyte candidates for magnesium batteries and identifies key areas for further optimization. We anticipate this review will be a valuable resource for researchers, guiding the development of advanced solid electrolytes for magnesium batteries.