Boron–Based Electrolytes for Rechargeable Magnesium Batteries: Biography and Perspective

Abstract Rechargeable magnesium batteries (RMBs) are a promising alternative in the post–lithium era for their high volumetric capacity, crustal abundance, and metallic safety. Electrolytes for RMBs have experienced a development process from the initial Grignard compound to today's diversified single magnesium salt. Among them, the boron‐based electrolyte plays a significant connecting link between the preceding and the following. This review retrospectively combed the origin and development course of boron–magnesium electrolyte and focuses on the application of three representatives: borohydride, boron‐center fluorinated alkoxylate, and closo–borane cluster. Fundamental understandings and typical concerns correlative with the Mg−B electrolyte designs are highlighted and briefly discussed. Finally, future direction and possible proposals for practical Mg−B electrolytes are put forward.