Structural engineering of α-MnO2 cathode by Ag plus incorporation for high capacity aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered as renewable alternatives to lithium-ion batteries (LIBs) for large-scale energy storage applications due to their intrinsic safety, cost-effectiveness, and environ-mental friendliness. The design and development of cathode materials are the main challenges to realizing the full potential of aqueous ZIBs. Here, we design Ag0.4Mn8O16 nanorods by structural engineering of alpha-MnO2 via Ag + incorporation for ZIBs cathode material. The sliver species are well dispersed in the tunnels of alpha-MnO2, which results in higher surface area, smaller nanorods, and oxygen vacancies in the Ag0.4Mn8O16 structure. Along with the redox activity of Ag+, reversible co-insertion/extraction of H+/Zn2+ ions in Ag0.4Mn8O16 followed by the formation of ZnxAg0.4-xMn8O16/MnOOH are observed. The generation of in-situ silver matrix greatly enhances the electronic conductivity, which, together with the reversible Ag0.4Mn8O16 structure, reveals an excellent electrochemical performance such as excellent rate capability, the high specific capacity of 306 mAh g-1 at 0.1 A g-1, and long-term cycling life over 800 cycles at 1 A g-1 compared to alpha-MnO2 (227 mAh g-1 at 0.1 A g-1). This work provides the design of cathode materials and the corresponding energy storage mechanism options for rechargeable aqueous ZIBs.