Carboxyl‐CNTs Act as “Defensive Shield” to Boost Proton Insertion for Stable and Fast‐Charging Aqueous Zn‐Mn Batteries

Abstract Proton insertion mechanism with fast reaction kinetics is attracting more and more attention for high‐rate and durable aqueous Zn─MnO2 batteries. However, hydrated Zn2+ insertion reaction accompanied with Jahn–Teller effect and Mn3+ disproportionation generally leads to sluggish rate capability and irreversible structure transformation. Here, carboxyl‐carbon nanotubes supported α‐MnO2 nanoarrays (C─MnO2) cathode is successfully fabricated by a convent grinding process for high‐performance Zn batteries. Specifically, the carboxyl‐carbon nanotubes (CNTs) skeleton endows α‐MnO2 with a shorter ion diffusion route and more active sites for proton adsorption, benefiting to the fast electron transport and reversible structure evolution of MnO2. More importantly, electronegative carboxyl groups and Mn─O─C interfacial bonds can effectively restrain Mn2+ dissolution and shuttle for improved structural integrity and redox reactivity. Consequently, the C─MnO2 cathode exhibits high capacity, superior rate capability, and outstanding cycling stability over 10 000 cycles. Even at ultra‐high mass loading (20 mg cm−2), the Zn//C─MnO2 punch cell displays excellent capacity (202 mAh) and 94.5% capacity retention after 114 cycles, providing new insights for the practical application of advanced Zn‐Mn batteries.