Salt Template-Assisted Preparation of C–O Bond Domain-Limited MnO@C Nanosheet Cathodes for Aqueous Zinc-Ion Batteries

Cost-effective and safe aqueous zinc-ion batteries (AZIBs) are considered strong competitors to lithium-ion batteries. Recently, MnO has been found to have potential Zn-ion storage capabilities. Nevertheless, the low Zn2+ ion diffusion kinetics, significant volume expansion during Zn2+ intercalation, and poor conductivity present challenges for MnO-based cathodes in practical applications in AZIBs. To address these challenges, this study proposes a C–O bond domain-limited MnO@C nanosheet material prepared by a salt template strategy as an effective cathode for AZIBs. MnO nanoparticles are coated with a self-assembled C shell through the confinement effect of the C–O bond to mitigate the volume expansion of MnO nanoparticles during Zn2+ intercalation while enhancing the charge transfer between the carbon shell and MnO nanoparticles through the C–O–Mn bond. Carbon-coated MnO (MnO@C) nanospheres self-assemble into porous 2D nanosheets with the assistance of the salt template to improve the electron and Zn ion transfer rate along the axial direction. Benefiting from the ingenious structural design, the prepared C–O bond domain-limited MnO@C nanosheets exhibit excellent performance as cathodes for AZIBs. The reversible specific capacities of the prepared cathode material reach 339.1 mAh g–1 after 1000 cycles at 2 A g–1 and 133.5 mAh g–1 after 3000 cycles at 5 A g–1 under room temperature. Moreover, these values are still maintained at 162.1 mAh g–1 at 10 °C and 154.8 mAh g–1 at 0 °C under a current density of 0.5 A g–1. This work would contribute to advancing the practical applications of MnO-based cathodes in AZIBs.