Oxygen Vacancies Boosted Proton Intercalation Kinetics for Aqueous Aluminum–Manganese Batteries

Aluminum-ion batteries have garnered an extensive amount of attention due to their superior electrochemical performance, low cost, and high safety. To address the limitation of battery performance, exploring new cathode materials and understanding the reaction mechanism for these batteries are of great significance. Among numerous candidates, multiple structures and valence states make manganese-based oxides the best choice for aqueous aluminum-ion batteries (AAIBs). In this work, a new cathode consists of γ-MnO₂ with abundant oxygen vacancies. As a result, the electrode shows a high discharge capacity of 481.9 mAh g^–1 at 0.2 A g^–1 and a sustained reversible capacity of 128.6 mAh g^–1 after 200 cycles at 0.4 A g^–1. In particular, through density functional theory calculation and experimental comparison, the role of oxygen vacancies in accelerating the reaction kinetics of H⁺ has been verified. This study provides insights into the application of manganese dioxide materials in aqueous AAIBs.