Architecting a High Specific Energy Aqueous Aluminum–Manganese Battery

Aluminum-based aqueous batteries are considered one of the most promising candidates for the upcoming generation energy storage systems owing to their high mass and volume-specific capacity, high stability, and abundant reserves of Al. But the side reactions of self-corrosion and passive film severely impede the advancement of aluminum batteries. Besides, the ideal matched electrolyte system and cathode working mechanism still need to be explored. Herein, a high specific energy aqueous aluminum–manganese battery is constructed by interfacial modified aluminum anode, high concentration electrolyte and layered manganese dioxide cathode. At the anode, in addition to boosting the wettability of the interface between the electrolyte and aluminum electrode, the altered surface of aluminum anode can also retard side reactions. At the same time, high concentration electrolyte (5 mol L⁻¹ Al(OTF)₃) with a broad electrochemical window allows the battery system to attain a specific capacity of 452 mAh g⁻¹ at 50 mA g⁻¹ and an energy density of 542 Wh kg⁻¹, with greatly increased cycle stability. At the cathode, the mechanism investigation reveals that δ-MnO₂ is reduced to soluble Mn²⁺ during the first cycle discharge, whereas Al_xMn_(1−x)O₂ generates during the charging process, acting as a highly reversible active material in the succeeding cycle. This comprehensive study paves the way for the development of aluminum-based energy storage devices.