Enhanced Electrochemical Performance of Aqueous Zinc‐Ion Batteries With Porous Basil‐Derived Carbon and Nanostructured MnO₂ Composite Cathodes

ABSTRACT This study introduces a novel composite cathode for aqueous zinc‐ion batteries (ZIBs), leveraging porous basil‐derived activated carbon (BAC) and nanostructured manganese dioxide (MnO 2 ) synthesized through a one‐step hydrothermal process. For the first time, basil‐derived carbon is integrated with MnO 2 , resulting in enhanced electrochemical performance. The MnO 2 /BAC composite delivers a remarkable specific capacity of 237 mAh/g at 0.5 A/g, along with an energy density of 314 Wh/kg and a power density of 0.66 kW/kg, outperforming cathodes made from pristine MnO 2 or BAC. These improvements stem from reduced particle size and a synergistic balance of capacitive and diffusive charge storage mechanisms. Density functional theory calculations corroborate the experimental results, revealing the composite's superior quantum capacity (158.7 µC/cm 2 ) and quantum capacitance (80.4 µF/cm 2 ). Stability assessments highlight excellent cycle life, with > 90% capacity retention and 100% Coulombic efficiency over 300 cycles. The exceptional performance is attributed to the material's unique nanostructure, high surface area (1090 m 2 /g), and optimized porosity. Additionally, practical applications of ZIBs in pouch cell form using the MnO₂/BAC cathode are demonstrated, showcasing its capability to power a toy car over a satisfactory distance. This study establishes a new benchmark for sustainable and cost‐effective cathode materials, significantly advancing ZIB technology for high‐efficiency energy storage applications.