Ice crystal sublimation for easily producing MnO 2 cathodes with hierarchically porous structure and enhanced cyclic reversibility.

The charge/discharge performance of rechargeable aqueous zinc ion batteries (RAZIBs) at high currents is often unsatisfactory due to the cathode preparation process and the use of hydrophobic binders. By adding freeze-drying treatment to the preparation process of the cathodes, MnO 2 cathodes with hierarchically porous structures are obtained, which provide additional channels for ion transfer, thus greatly enhancing the charge/discharge performance in aqueous Zn-MnO 2 batteries.