A Shuttle-Catalysis Strategy Coupled with 3D Conductive Scaffolds for Ultrafast and Long-Lifespan MnO2/Mn2+ Conversion Chemistry.

Aqueous rechargeable batteries relying on the two-electron MnO2/Mn2+ deposition/dissolution chemistry offer a high theoretical capacity (616 mAh g-1). However, their practicality is hampered by the disproportionation of Mn3+ intermediates and the irreversible buildup of electrochemically inert MnO2 deposits, which severely compromise the reversibility of the MnO2/Mn2+ conversion process and undermine long-term cycling stability. To overcome these issues, we propose an Fe2+-induced shuttle-catalysis strategy with a rationally designed three-dimensional (3D) conductive carbon scaffold. Specifically, Fe2+ was introduced as a redox mediator to catalytically accelerate MnO2 dissolution via MnO2 + 2Fe2+ + 4H+ → Mn2+ + 2Fe3+ + 2H2O, enabling high MnO2/Mn2+ conversion efficiency. Simultaneously, a carbon nanotube‑decorated carbon cloth serves as the conductive current collector, offering abundant disproportionation sites for the diffused Mn3+ and sufficient electron‑transport pathways to guide uniform MnO2 growth. As a result, the optimized MnO2/Mn2+ cathode achieves exceptional stability over 7000 cycles at 3 mAh cm-2 and remarkable rate capability with negligible capacity loss at 60 mA cm-2. When paired with a Sn anode in a full‑cell configuration, the battery exhibits stable cycling for more than 1800 cycles, and practical functionality demonstrated by powering a light-emitting diode.