Understanding of the charge storage mechanism of MnO2-based aqueous zinc-ion batteries: Reaction processes and regulation strategies

Though secondary aqueous Zn ion batteries (AZIBs) have been received broad concern in recent years, the development of suitable cathode materials of AZIBs is still a big challenge. The MnO2 has been deemed as one of most hopeful cathode materials of AZIBs on account of some extraordinary merits, such as richly natural resources, low toxicity, high discharge potential, and large theoretical capacity. However, the crystal structure diversity of MnO2 results in an obvious various of charge storage mechanisms, which can cause great differences in electrochemical performance. Furthermore, several challenges, including intrinsic poor conductivity, dissolution of manganese and sluggish ion transport dynamics should be conquered before real practice. This work focuses on the reaction mechanisms and recent progress of MnO2-based materials of AZIBs. In this review, a detailed review of the reaction mechanisms and optimal ways for enhancing electrochemical performance for MnO2-based materials is proposed. At last, a number of viewpoints on challenges, future development direction, and foreground of MnO2-based materials of aqueous zinc ions batteries are put forward. This review clarifies reaction mechanism of MnO2-based materials of AZIBs, and offers a new perspective for the future invention in MnO2-based cathode materials, thus accelerate the extensive development and commercialization practice of aqueous zinc ions batteries.