Al doped manganous oxide for high-performance aqueous Zn-ion batteries

MnO has been proved to be a feasible cathode material for aqueous zinc ion batteries, but the absence of tunnel structure in MnO and strong electrostatic interaction between MnO and guest ions make Zn/MnO batteries exhibit poor performance. To remedy this intrinsic defect, we propose a strategy of Al doping to modify MnO, which not only introduces abundant Mn vacancies to improve Zn2+ diffusion, but also increases the specific surface area and pore size of MnO to enhance the wettability of cathode towards electrolyte. We also found that Al-MnO converted into ramsdellite-MnO2 (R-MnO2) during charge/discharge, which further suppresses Mn2+ dissolution. Employing such Al-MnO as cathode material, the assembled aqueous zinc ion batteries (ZIBs) shows high specific capacity (345 mAh g-1 at 0.1 A g-1) and possesses a long-term capacity retention of about 89% over 500 cycles at 1.0 A g-1. This work offers novel insights into the cathode design for low cost and high safety aqueous ZIBs with excellent electrochemical performance.