Suppressing Manganese Dissolution in Potassium Manganate with Rich Oxygen Defects Engaged High‐Energy‐Density and Durable Aqueous Zinc‐Ion Battery

Abstract The manganese dissolution leading to sharp capacity decline as well as the sluggish reaction kinetic are still major issues for manganese‐based materials as aqueous zinc‐ion batteries (ZIBs) cathodes. Here, a potassium‐ion‐stabilized and oxygen‐defect K 0.8 Mn 8 O 16 is reported as a high‐energy‐density and durable cathode for neutral aqueous ZIBs. A new insight into suppressing manganese dissolution via incorporation of K + ions to intrinsically stabilize the Mn‐based cathodes is provided. A comprehensive study suggests that oxygen defects improve electrical conductivity and open the MnO 6 polyhedron walls for ion diffusion, which plays a critical role in the fast reaction kinetics and capacity improvement of K 0.8 Mn 8 O 16 . In addition, direct evidence for the mechanistic details of simultaneous insertion and conversion reaction based on H + ‐storage mechanism is demonstrated. As expected, a significant energy output of 398 W h kg −1 (based on the mass of cathode) and an impressive durability over 1000 cycles with no obvious capacity fading are obtained. Such a high‐energy Zn‐K 0.8 Mn 8 O 16 battery, as well as the basic understanding of manganese dissolution and oxygen defects may open new opportunities toward high‐performance aqueous ZIBs.