Oxygen Vacancy-Driven High-Performance V₂O₅ Cathodes for Aqueous Manganese Metal Batteries

Aqueous batteries are an emerging next-generation technology for large-scale energy storage. Among various metal-ion systems, manganese-based batteries have attracted significant interest due to their superior theoretical energy density over zinc-based battery systems. This study demonstrates oxygen vacancy-engineered vanadium oxide (V₂O_4.85) as a high-performance cathode material for aqueous manganese metal batteries. The V₂O_4.85 cathode had a discharge capacity of 212.6 mAh g⁻¹ at 0.1 A g⁻¹, retaining 89.5% capacity after 500 cycles. Oxygen vacancies enhanced ion diffusion and reduced migration barriers, facilitating both Mn²⁺ and H⁺ ion intercalation. Proton intercalation dominated charge storage, forming Mn(OH)₂ layers, whereas Mn²⁺ contributed to surface-limited reactions. Furthermore, manganese metal batteries had a significantly higher operating voltage than that of aqueous zinc battery systems. Despite challenges with hydrogen evolution reactions at the Mn metal anode, this study underscores the potential of manganese batteries for future energy storage systems.