Cr-doping δ-MnO2 as the cathode material for aqueous zinc-ion batteries

Manganese-based aqueous zinc-ion batteries are considered to be one of the most promising candidates owing to its abundant resources, environmental friendliness and high safety. However, some severe problems associated with cathode are mainly plagued by Mn (III) disproportionation and Jahn-Teller distortion, leading to undesired manganese dissolution and reduced their cycle life. Herein, Cr-doped delta-MnO2 is synthesized by a simple hydrothermal method. This study demonstrates how Cr-doping addresses these challenges by narrowing the lattice spacing between MnO2 layers, promoting self-confinement, and mitigating Mn2+ dissolution. As a result, Crdoped delta-MnO2 exhibits enhanced crystal structure stability, with superior capacity retention of 65.80 % compared to 51.53 % for pristine delta-MnO2 after 300 cycles at 500 mA/g. Our findings provide an alternative avenue for mitigating Mn dissolution, laying the groundwork for the adoption of Zn/MnO2 batteries.