Charge storage mechanism of MOF-derived Mn₂O₃ as high performance cathode of aqueous zinc-ion batteries

Aqueous Zinc-ion batteries (ZIB) are attracting immense attention because of their merits of excellent safety and quite cheap properties compared with lithium-ion batteries (LIB). Manganese oxide is one of the most important cathode materials of ZIB. In this paper, α-Mn₂O₃ used as cathode of ZIB is synthesized via Metal-Organic Framework (MOF)-derived method, which delivers a high specific capacity of 225 mAh g⁻¹ at 0.05 A g⁻¹ and 92.7 mAh g⁻¹ after 1700 cycles at 2 A g⁻¹. The charge storage mechanism of α-Mn₂O₃ cathode is found to greatly depend on the discharge current density. At lower current density discharging, the H⁺ and Zn²⁺ are successively intercalated into the α-Mn₂O₃ before and after the “turning point” of discharge voltage and their discharging products present obviously different morphologies changing from flower-like to large plate-like products. At a higher current density, the low-voltage plateau after the turning point disappears due to the decrease of amount of Zn²⁺ intercalation and the H⁺ intercalation is dominated in α-Mn₂O₃. This study provides significant understanding for future design and research of high-performance Mn-based cathodes of ZIB.