Interfacial and structural optimization of graphene wrapped β-MnO₂ nanorod cathodes for long-life aqueous zinc-ion...

Aqueous zinc-ion batteries (AZIBs) as promising candidates for grid-scale storage are constrained by the poor conductivity and structural instability of manganese dioxide (MnO₂) cathodes during cycling. Herein, we report a rationally designed cathode comprising β-MnO₂ nanorods intimately decorated with reduced graphene oxide (β-MnO₂@rGO) through an in-situ hydrothermal and thermal activation process. The one-dimensional β-MnO₂ nanorods provide shortened diffusion pathways for H⁺/Zn²⁺ions, while the conformal rGO network establishes a three-dimensional conductive skeleton that enhances electronic transport and buffers volumetric expansion during cycling. X-ray photoelectron spectroscopy (XPS) confirms the formation of robust Mn-O-C interfacial bonds, which facilitate charge transfer and mitigate manganese dissolution. The optimized β-MnO₂@rGO-30 exhibits a high reversible specific capacity of 387 ± 3.0 mAh g^-1 at 0.1 A g^-1 and maintains 89 ± 1% capacity retention after 6000 cycles at 1.0 A g^-1. A sequential insertion mechanism, beginning with H⁺ intercalation followed by Zn²⁺ storage, with excellent structural reversibility, is elucidated by ex-situ spectroelectrochemical analysis. This work provides a viable strategy for designing high-performance MnO₂-based cathodes through synergistic nanoengineering and conductive hybridization for advanced AZIBs.