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

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.