Designing binary electrolyte additive mixtures for achieving high-performance aqueous Mg-air batteries

Developing cost-effective and high-discharge performance electrolyte additives is essential for the application of aqueous Mg-air batteries. However, most individual additives cannot simultaneously optimize both the cell voltage and anode efficiency, resulting in only a mediocre specific energy. Herein, we aim to elucidate the limitations of individual electrolyte additives and introduce an efficient strategy that leverages binary mixture of electrolyte additives to overcome these challenges. The results indicate that binary electrolyte additive mixtures, selected according to the guidelines formulated herein, effectively inhibit the hydrogen evolution reaction, chunk effect, and oxygen reduction reaction of Mg anode. The self-corrosion mechanism was estimated with the assistance of in-operando scanning microprobe techniques. Moreover, employing binary electrolyte additive mixtures simultaneously enhances anode efficiency and increases cell voltage in aqueous Mg–air batteries, enabling a breakthrough specific energy of 2587 Wh kg −1 — the highest reported to date at an applied current density of 5 mA cm −2 . This work paves the way for the development of high specific energy Mg–air batteries through rational design of binary electrolyte additive systems.