Porous Activated Carbon Induced Confined Synthesis β‐MnO ₂ Nanorods for High‐Capacity Aqueous Zinc‐Ion Batteries

Manganese‐dioxide (MnO 2 ) is one of the most attractive cathode materials for aqueous zinc‐ion batteries (AZIBs) owing to its high theoretical capacity and high safety. Herein, β‐MnO 2 nanorods were synthesized for the first time by introducing porous activated carbon (AC) as a structural directing agent. During the hydrothermal synthesis process, the α‐MnO 2 nanowires or β‐MnO 2 nanorods (AC‐β‐MnO 2 ) were synthesized via with or without added AC. The β‐MnO 2 was preferential nucleation in AC pore toward to form nanorods and finally with a carbon film on the surface. Therefore, this AC‐β‐MnO 2 can inhibit the dissolution of manganese and improve the conductivity in AZIBs. As a result, the AC‐β‐MnO 2 provide a specific capacity of 355.3 mAh g −1 at 0.1 A g −1 and exhibits high cycle stability with capacity retention rates at 96% after 200 cycles at 0.5 A g −1 , which revealed superior performance than α‐MnO 2 nanowires. Moreover, density functional theory (DFT) calculations confirm that the d ‐band center of Mn in AC‐β‐MnO 2 moves up, which enhances the conductivity and the increase in absolute value of adsorption energy enhances the adsorption capacity for Zn 2+ . This work provides a new perspective for developing high‐capacity MnO 2 cathode materials in AZIBs through confined synthesis.