A comprehensive review of strategies to augment the performance of MnO2 cathode by structural modifications for aqueous zinc ion battery.

The development of new cathode materials for aqueous zinc ion batteries (AZIBs) is a critical step toward developing robust and large-scale electrochemical energy conversion and storage systems. Recent studies in this field have witnessed the emergence of manganese-based oxide cathode materials, with manganese dioxide (MnO 2) growing as a promising one owing to its high capacity, impressive energy density, high operating voltage, and cost-effectiveness. Nevertheless, the practical utilization of MnO 2 cathodes confronts substantial challenges like sluggish diffusion kinetics, low electronic conductivity, and structural instability during the cycling process. In this review, we present a thorough examination of the key approaches adopted by researchers to address the prevailing challenges and improve the MnO 2 cathode's electrochemical performance. We first discuss the structures of different MnO 2 polymorphs, followed by various synthesis techniques commonly employed to obtain electrochemically engineered MnO 2. Then we discuss the challenges associated with MnO 2 cathode when employed in AZIB. Next we thoroughly investigate three main strategies (preintercalation, defect engineering, and composite formation) opted to enhance MnO 2 performance. In conclusion, we outline the challenges and prospects inherent in these strategies, to further improve MnO 2 performance thereby advancing its utility as a cathode material for AZIB. [Display omitted] • MnO 2 is the most promising cathode material for zinc-ion battery. • It offers high theoretical capacity and open circuit voltage. • Poor structural stability and slow reaction kinetics hinder its utility as a cathode. • Methods to improve MnO 2 are: pre-intercalation, defect engineering and composites. • This is a consolidated and a comprehensive review of all the strategies adopted. [ABSTRACT FROM AUTHOR]