Hierarchically Mesoporous Graphene Networks Modulate Homogeneous Two-Electron Redox Chemistry for Highly Reversible and Stable Zinc-Air Batteries

The emerging two-electron (2e⁻) redox Zinc-air batteries (ZABs) in neutral electrolytes have attracted substantial research interest due to their better reversibility and stability compared to alkaline ZABs. However, the generation of nonconductive discharge products (ZnO₂) raises kinetics and stability challenges for the design of air cathodes. Herein, a redox-homogenization electrochemistry approach is reported to accelerate the reversible conversion of ZnO₂ and promote the 2e⁻/O₂ reaction. The conductive graphene framework, featuring ultrahigh surface areas and high electrical/ionic conductivity, effectively reduces local current densities, thus effectively homogenizing the 2e⁻ redox reaction. Additionally, the hydrophobic 3D network not only diminishes the nucleation barrier but also restricts the growth of ZnO₂ within the mesopores, achieving the homogenization of discharge products and robust reaction kinetics. The fabricated neutral ZABs exhibit a low polarization of 0.43 V and excellent stability beyond 580 h at 0.5 mA cm⁻², most importantly, a benchmark energy efficiency of 75.4% at 0.1 mA cm⁻² and 59.5% at 10 mA cm⁻². This work provides a blueprint for constructing advanced carbon cathodes for metal-air batteries.