Towards high-performance aqueous Zn–MnO2 batteries: Formation mechanism and alleviation strategies of irreversible inert phases

Rechargeable aqueous Zn–MnO2 batteries have been developed rapidly in decades because of the low cost, rich resources, low toxicity, and high working potential. Unfortunately, MnO2-based cathode materials also suffer from poor conductivity, Mn dissolution, sluggish ion diffusion dynamics and bad structure stability, resulting in low reversible capacity and inferior cyclability. Especially, the formation of irreversible inert phase on the surface of electrode can inhibits the further electrochemical reactions between MnO2 and electrolyte, and result in the failure of Zn–MnO2 battery. A comprehensive understanding of formation mechanism for the irreversible inert phases will act a vital role in developing high-performance Zn–MnO2 battery. This review mainly concentrates on recent progress of the formation mechanism and solutions of irreversible inert phases of Zn–MnO2 battery. A comprehensive optimization strategy of alleviating the generation of irreversible inert phase to boost the electrochemical property of MnO2-based materials is put forward. This review clarifies the formation mechanism of irreversible inert phase in the MnO2-based material for aqueous Zn–MnO2 battery, and put forward the development prospects of MnO2-based cathode materials for AZIBs. This provides new perspectives for the fabrication of MnO2-based cathode materials in the future, thus accelerating the extensive development and commercial application of aqueous Zn–MnO2 battery.