An activated Prussian blue interphase enhancing H+ storage of MnO2 cathode for aqueous zinc ion battery

To resolve the Mn dissolution and sluggish kinetics issues of MnO2 cathode for aqueous zinc ion battery, designing the interphase with crystal structure containing abundant water molecules has been recently utilized to simultaneously enhance the H+ storage and suppress the Mn dissolution. In this work, a Prussian blue (PB) interphase is synthesized in-situ on a MnO2 cathode, which is introduced with more crystal water molecules by an activation upon discharge. Investigation verifies that during the activation process, H+ insertion irreversibly introduces more structural water into the PB interphase, and irreversible Zn2+ insertion enhances the stability of the PB interphase. As a result, the activated PB interphase with abundant structural water facilitates the realization of Grotthuss proton transport and significantly enhances the H+ storage capacity of the MnO2 cathode, which renders the MnO2 cathode with superior rate performance (343 mAh g-1 at 0.2Ag-1 and 91 mAh g-1 at 20Ag-1) and excellent cycle performance (80.5% capacity retention after 2000 cycles at 5Ag-1).