Doping Engineering in Manganese Oxides for Aqueous Zinc-Ion Batteries

Manganese oxides (Mn_xO_y) are considered a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to their high theoretical specific capacity, various oxidation states and crystal phases, and environmental friendliness. Nevertheless, their practical application is limited by their intrinsic poor conductivity, structural deterioration, and manganese dissolution resulting from Jahn-Teller distortion. To address these problems, doping engineering is thought to be a favorable modification strategy to optimize the structure, chemistry, and composition of the material and boost the electrochemical performance. In this review, the latest progress on doped Mn_xO_y-based cathodes for AZIBs has been systematically summarized. The contents of this review are as follows: (1) the classification of Mn_xO_y-based cathodes; (2) the energy storage mechanisms of Mn_xO_y-based cathodes; (3) the synthesis route and role of doping engineering in Mn_xO_y-based cathodes; and (4) the doped Mn_xO_y-based cathodes for AZIBs. Finally, the development trends of Mn_xO_y-based cathodes and AZIBs are described.