Understanding the Role of Cathode Solubility in Magnesium Batteries: A Case Study of Substituted Bis‐Benzoquinones

Rechargeable magnesium batteries (RMBs) have emerged as a promising alternative to lithium‐ion batteries owing to their high energy density, enhanced safety, and cost‐effectiveness. However, critical challenges remain for their commercial viability, particularly in the development of suitable cathode materials. In this study, substituted bis‐benzoquinones as multielectron organic cathodes for magnesium batteries are investigated. These compounds are synthesized via a simple and scalable route, with competitive projected manufacturing costs. A systematic investigation of their solubility in magnesium‐based electrolytes reveals a strong dependence on the chemical nature of the magnesium salt. Magnesium cells incorporating substituted bis‐benzoquinones demonstrate high specific capacities of up to 419 mAh g −1 at an average voltage of 1.7 V versus Mg 2+ /Mg, corresponding to a material‐level specific energy of 600 Wh kg −1 . Furthermore, these compounds demonstrate excellent rate capability, delivering full capacity at 5C and retaining 70% of their capacity at 2 °C. These results underscore the potential of substituted bis‐benzoquinones for cost‐effective, high‐energy, and fast‐charging RMBs.