Heterostructure Engineering of MnO@C Nanocomposite for High-Performance Aqueous Zinc-Ion Batteries

For aqueous zinc-ion batteries (AZIBs), manganese-based cathodes have risen to prominence as a highly attractive choice, driven by their high theoretical capacity, low cost, eco-friendly nature, and multiple oxidation states. Yet, the low intrinsic conductivity, slow Zn2+ diffusion, and insufficient rate capability hinder the practical application. Herein, a rice-grain-shaped MnO@C nanocomposite featuring a robust heterogeneous interface was formed by a facial hydrothermal method for AZIBs. The heterojunction interface between MnO and the carbon layer facilitates ion/electron transfer, suppresses Mn2+ dissolution, and enhances structural stability. Consequently, the MnO@C electrode delivers a superior specific capacity of 219.7 mAh g–1 at 0.2 A g–1 after 100 cycles. Moreover, the per-cycle capacity fading rate is merely 0.0077%, even after 1000 cycles at 1.0 A g–1. A series of characterization tests further confirmed the interface effect. Via ex situ XRD and SEM, the Zn ion storage mechanism can be confirmed. This study establishes an effective carbon-coating strategy to construct advanced manganese-based cathodes, providing design principles for the development of high-performance AZIBs.