Construction of MnO2 with oxygen defects as cathode material for aqueous zinc ion batteries

In recent years, aqueous zinc-ion batteries (AZIBs) have been rapidly developed and are favored by the public as a future large-scale energy storage system. Manganese-based compounds with multiple valence states and high electrochemical activity have been extensively investigated as cathodes for AZIBs due to their abundant reserves and high theoretical capacity. However, some problems hinder their application in AZIBs, such as low conductivity and sluggish kinetics. Defect engineering has been verified as an effective method to alleviate the above limitations. In this work, manganese oxide with oxygen defects (O-d-MnO2) was successfully constructed and characterized by XRD, SEM, XPS, and TEM. Surface oxygen defects increase ion active transfer sites and improve electronic conductivity. Compared with MnO2, O-d-MnO2 produced more localized electrons which could improve the electrochemical performance as cathodes for AZIBs. The discharge specific capacity of O-d-MnO2 reaches 307.9 mAh g(-1) in the first cycle at a current density of 0.1 A g(-1) and maintains at 100.5 mAh g(-1) at a current density of 10.0 A g(-1). After 1000 cycles, the discharge specific capacity can still reach 82.5 mAh g(-1) and the capacity retention rate is 82.1%.